JDK环境变量配置及常用Java工具类指南

2026-06-28阅读 0热度 0

其他

一. JDK环境变量配置

1. 位置

配置JDK环境变量第一步：找到入口。在桌面右键点击“我的电脑”（或“此电脑”），选择“属性”，接着进入“高级系统设置”，最后点击“环境变量”按钮。

2. 作用域

环境变量窗口里会看到两个区域：用户变量和系统变量。它们的作用域完全不同——用户变量只对当前登录用户生效，而系统变量则影响整个计算机上的所有用户。

3. 配置内容

接下来就是添加具体的变量了。需要添加以下三个变量，如果变量已经存在，直接在原有值的后面追加即可。注意每一项之间用英文分号隔开。

变量名	变量值
JA VA_HOME	D:Ja vajdk1.8;
PATH	%JA VA_HOME%bin;
CLASSPATH	%JA VA_HOME%libtools.jar;

二. Ja va后台获得客户端IP

获取客户端真实IP是个常见需求，尤其是在使用了反向袋里（比如Nginx）的情况下，简单的 request.getRemoteAddr() 就不够用了。这时候需要从请求头里一层层地找。直接看代码，逻辑很清晰：

import com.alibaba.druid.util.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import ja vax.servlet.http.HttpServletRequest;

/**
 * 获取客户端IP地址
 */
public class IPUtils {
    private static Logger logger = LoggerFactory.getLogger(IPUtils.class);

    /**
     * 获取客户端IP地址
     */
    public static String getIpAddr(HttpServletRequest request) {
        String ip = null;
        try {
            ip = request.getHeader("x-forwarded-for");
            if (StringUtils.isEmpty(ip) || "unknown".equalsIgnoreCase(ip)) {
                ip = request.getHeader("Proxy-Client-IP");
            }
            if (StringUtils.isEmpty(ip) || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
                ip = request.getHeader("WL-Proxy-Client-IP");
            }
            if (StringUtils.isEmpty(ip) || "unknown".equalsIgnoreCase(ip)) {
                ip = request.getHeader("HTTP_CLIENT_IP");
            }
            if (StringUtils.isEmpty(ip) || "unknown".equalsIgnoreCase(ip)) {
                ip = request.getHeader("HTTP_X_FORWARDED_FOR");
            }
            if (StringUtils.isEmpty(ip) || "unknown".equalsIgnoreCase(ip)) {
                ip = request.getRemoteAddr();
            }
        } catch (Exception e) {
            logger.error("IPUtils ERROR ", e);
        }
        return ip;
    }
}

三. 无参获取Request和Response

有时候在工具类或非Controller层需要拿到Request对象，但方法签名里没有传参。Spring提供了一个很好用的 RequestContextHolder，可以直接从当前线程绑定中获取。实现如下：

import ja vax.servlet.http.HttpServletRequest;
import ja vax.servlet.http.HttpServletResponse;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

public class HttpContextUtils {
    /**
     * 获取Request
     */
    public static HttpServletRequest getHttpServletRequest() {
        if(RequestContextHolder.getRequestAttributes()==null){
            return null;
        }
        return ((ServletRequestAttributes)RequestContextHolder.getRequestAttributes()).getRequest();
    }

    /**
     * 获取Response
     */
    public static HttpServletResponse getHttpServletResponse() {
        if(RequestContextHolder.getRequestAttributes()==null){
            return null;
        }
        return ((ServletRequestAttributes)RequestContextHolder.getRequestAttributes()).getResponse();
    }
}

四. Ja va代码行数统计

想知道项目里写了多少行代码？这个小工具可以帮你统计Ja va文件的代码行数、注释行数和空白行数。需要注意的是，这个类需要放在 src/test/ja va 目录下才能正常工作。核心思路就是递归扫描目录，然后逐行分析。

import ja va.io.BufferedReader;
import ja va.io.File;
import ja va.io.FileNotFoundException;
import ja va.io.FileReader;
import ja va.io.IOException;
import ja va.util.ArrayList;

public class CodeCounter {
    static long files = 0;
    static long codeLines = 0;
    static long commentLines = 0;
    static long blankLines = 0;
    static ArrayList fileArray = new ArrayList();

    public static ArrayList getFile(File f) {
        File[] ff = f.listFiles();
        for (File child : ff) {
            if (child.isDirectory()) {
                getFile(child);
            } else
                fileArray.add(child);
        }
        return fileArray;
    }

    private static void count(File f) {
        BufferedReader br = null;
        boolean flag = false;
        try {
            br = new BufferedReader(new FileReader(f));
            String line = "";
            while ((line = br.readLine()) != null) {
                line = line.trim();
                if (line.matches("^[ ]*$")) {
                    blankLines++;
                } else if (line.startsWith("//")) {
                    commentLines++;
                } else if (line.startsWith("/*") && !line.endsWith("*/")) {
                    commentLines++;
                    flag = true;
                } else if (line.startsWith("/*") && line.endsWith("*/")) {
                    commentLines++;
                } else if (flag == true) {
                    commentLines++;
                    if (line.endsWith("*/")) {
                        flag = false;
                    }
                } else {
                    codeLines++;
                }
            }
            files++;
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (br != null) {
                try {
                    br.close();
                    br = null;
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static void main(String[] args) {
        String file = CodeCounter.class.getResource("/").getFile();
        String path = file.replace("target/test-classes", "src");
        ArrayList al = getFile(new File(path));
        for (File f : al) {
            if (f.getName().matches(".*.ja va$")){
                count(f);
                System.out.println(f);
            }
        }
        System.out.println("统计文件：" + files);
        System.out.println("代码行数：" + codeLines);
        System.out.println("注释行数：" + commentLines);
        System.out.println("空白行数：" + blankLines);
    }
}

五. 判断设备类型(PC, 手机等), 浏览器类型(IE, Google等)

在Web开发中经常需要根据用户设备返回不同的页面，比如手机端和PC端分别渲染。推荐一个成熟的第三方库 UserAgentUtils，它能从User-Agent中解析出操作系统、浏览器和设备类型。先引入依赖：

1. Ma ven导包如下


    eu.bitwalker
    UserAgentUtils
    1.21

2. 工具类如下

import ja vax.servlet.http.HttpServletRequest;
import eu.bitwalker.useragentutils.Browser;
import eu.bitwalker.useragentutils.DeviceType;
import eu.bitwalker.useragentutils.UserAgent;

public class UserAgentUtils {
    public static UserAgent getUserAgent(HttpServletRequest request) {
        return UserAgent.parseUserAgentString(request.getHeader("User-Agent"));
    }

    public static DeviceType getDeviceType(HttpServletRequest request) {
        return getUserAgent(request).getOperatingSystem().getDeviceType();
    }

    public static boolean isComputer(HttpServletRequest request) {
        return DeviceType.COMPUTER.equals(getDeviceType(request));
    }

    public static boolean isMobile(HttpServletRequest request) {
        return DeviceType.MOBILE.equals(getDeviceType(request));
    }

    public static boolean isTablet(HttpServletRequest request) {
        return DeviceType.TABLET.equals(getDeviceType(request));
    }

    public static boolean isMobileOrTablet(HttpServletRequest request){
        DeviceType deviceType = getDeviceType(request);
        return DeviceType.MOBILE.equals(deviceType) || DeviceType.TABLET.equals(deviceType);
    }

    public static Browser getBrowser(HttpServletRequest request) {
        return getUserAgent(request).getBrowser();
    }

    public static boolean isLteIE8(HttpServletRequest request) {
        Browser browser = getBrowser(request);
        return Browser.IE5.equals(browser) || Browser.IE6.equals(browser) || Browser.IE7.equals(browser)
                || Browser.IE8.equals(browser);
    }
}

3. 进行拦截并根据需要进行处理

有了判断工具，下一步就是在Spring的拦截器里根据设备类型切换视图。比如手机或平板访问时，自动加上 mobile/ 前缀：

import ja vax.servlet.http.HttpServletRequest;
import ja vax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import org.apache.commons.lang3.StringUtils;

public class MobileInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
        if (modelAndView != null) {
            if (UserAgentUtils.isMobileOrTablet(request)
                    && !StringUtils.startsWithIgnoreCase(modelAndView.getViewName(), "redirect:")) {
                modelAndView.setViewName("mobile/" + modelAndView.getViewName());
            }
        }
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
    }
}

六. 根据日期生成目录

上传文件时，为了避免文件名重复，通常会用日期加时间戳来生成存储路径。下面这个工具类生成形如 2018/07/26/1532572300220 的路径：

import ja va.text.SimpleDateFormat;
import ja va.util.Date;

public class DirectoryUtils {
    public static String getDir() {
        StringBuilder sb = new StringBuilder("");
        Date date = new Date();
        SimpleDateFormat format = new SimpleDateFormat("yyyy/MM/dd");
        String path = format.format(date);
        long time = new Date().getTime();
        sb.append(path).append("/").append(time);
        return sb.toString();
    }
}

七. 根据附件名获得附件类型

当我们需要根据文件名后缀返回对应的类型（比如图片、文档、视频）时，可以借助 commons-io 的 FilenameUtils 来快速获取扩展名，然后做映射。

1. Ma ven导包


    commons-io
    commons-io
    2.6

2. 工具类

import org.apache.commons.io.FilenameUtils;

public class FileTypeUtils {
    public static String getFileType(String fileName) {
        if (fileName != null && !"".equals(fileName)) {
            String extension = FilenameUtils.getExtension(fileName);
            if ("jng".equalsIgnoreCase(extension) || "jpg".equalsIgnoreCase(extension)
                    || "png".equalsIgnoreCase(extension) || "gif".equalsIgnoreCase(extension)
                    || "jpeg".equalsIgnoreCase(extension) || "bmp".equalsIgnoreCase(extension)) {
                return "IMG";
            } else if ("txt".equalsIgnoreCase(extension)) {
                return "TXT";
            } else if ("doc".equalsIgnoreCase(extension) || "docx".equalsIgnoreCase(extension)) {
                return "DOC";
            } else if ("pdf".equalsIgnoreCase(extension)) {
                return "PDF";
            } else if ("xls".equalsIgnoreCase(extension) || "xlsx".equalsIgnoreCase(extension)) {
                return "XLS";
            } else if ("ppt".equalsIgnoreCase(extension) || "pptx".equalsIgnoreCase(extension)) {
                return "PPT";
            } else if ("zip".equalsIgnoreCase(extension)) {
                return "ZIP";
            } else if ("mp3".equalsIgnoreCase(extension)) {
                return "MP3";
            } else if ("mp4".equalsIgnoreCase(extension) || "flv".equalsIgnoreCase(extension)
                    || "a vi".equalsIgnoreCase(extension)) {
                return "A VI";
            } else if ("HTML".equalsIgnoreCase(extension)) {
                return "HTM";
            } else if ("VSD".equalsIgnoreCase(extension)) {
                return "VSD";
            } else {
                return "OTHER";
            }
        }
        return "";
    }
}

八. 附件上传下载

文件上传下载是每个Web项目几乎都会遇到的功能。下面这个工具类整合了上传和下载两个方法，上传时通过 System.getProperty("webPath") 获取部署根目录（需要在web.xml中配置），下载时支持中文文件名编码。

1. web.xml中需要加入如下代码


    webAppRootKey
    webPath

2. Ja va代码如下

import ja va.io.File;
import ja va.io.FileInputStream;
import ja va.io.IOException;
import ja va.io.InputStream;
import ja va.io.OutputStream;
import ja va.io.UnsupportedEncodingException;
import ja va.net.URLEncoder;
import ja vax.servlet.http.HttpServletRequest;
import ja vax.servlet.http.HttpServletResponse;
import org.springframework.web.multipart.MultipartFile;

public class FileUtils {
    public static String fileUpload(MultipartFile file, String subPath) {
        String basePath = System.getProperty("webPath");
        String path = basePath.replaceAll("\\\\", "/") + subPath;
        String finalPath = path + "/" + file.getOriginalFilename();
        File dir = new File(path);
        if (!dir.exists()) {
            dir.mkdirs();
        }
        try {
            file.transferTo(new File(finalPath));
        } catch (IOException e) {
            System.out.println("文件: " + file.getOriginalFilename() + "上传失败!");
            e.printStackTrace();
        }
        return finalPath;
    }

    public static boolean excelOutTemplate(HttpServletRequest request, HttpServletResponse response,
            String filePath, String fileShowName) {
        String localPath = request.getServletContext().getRealPath("/");
        String finalPath = localPath.endsWith("/") ? (localPath + filePath) : (localPath + "/" + filePath);
        File file = new File(finalPath);
        if (file.exists()) {
            try {
                response.addHeader("Content-Disposition",
                        "attachment;filename=" + URLEncoder.encode(fileShowName, "UTF-8"));
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }
            InputStream in = null;
            OutputStream out = null;
            try {
                in = new FileInputStream(finalPath);
                out = response.getOutputStream();
                int b;
                while ((b = in.read()) != -1)
                    out.write(b);
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    if (in != null)
                        in.close();
                    if (out != null)
                        out.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        } else {
            System.out.println("服务器文件已经不存在了!");
            return false;
        }
        return true;
    }
}

九. 获得UUID

生成唯一标识符最简单的方式就是UUID，去掉横线之后变成32位字符串，很多场景下用来做主键或文件名前缀。

import ja va.util.UUID;

public class IDUtils {
    public static String getId() {
        String id = UUID.randomUUID().toString();
        id = id.replace("-", "");
        return id;
    }
}

十. 自定义异常类

为了让业务异常和系统异常区分开，通常会定义一个自定义运行时异常。这里封装了 msg 和 code 两个字段，方便在全局异常处理器中统一返回。

public class RRException extends RuntimeException {
    private static final long serialVersionUID = 1L;
    private String msg;
    private int code = 500;

    public RRException(String msg) {
        super(msg);
        this.msg = msg;
    }

    public RRException(String msg, Throwable e) {
        super(msg, e);
        this.msg = msg;
    }

    public RRException(String msg, int code) {
        super(msg);
        this.msg = msg;
        this.code = code;
    }

    public RRException(String msg, int code, Throwable e) {
        super(msg, e);
        this.msg = msg;
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }
}

十一. 字符串首字母大写

有时候需要把字段名从驼峰转成首字母大写，比如生成getter/setter时。下面这个实现通过字符数组偏移量直接操作，效率很高。

public class StringUtils {
    public static String captureName(String name) {
        char[] cs=name.toCharArray();
        cs[0]-=32;
        return String.valueOf(cs);
    }
}

十二. List乱序与按照汉字拼音排序

做抽奖或随机展示时经常需要打乱List顺序，而汉字拼音排序则适用于按名字首字母分组等场景。注意拼音排序依赖 Collator 的 Locale.CHINA 参数。

import ja va.text.Collator;
import ja va.util.ArrayList;
import ja va.util.Collections;
import ja va.util.Comparator;
import ja va.util.List;
import ja va.util.Random;

public class ListUtils {
    public static  List randomList(List sourceList) {
        if (sourceList == null || sourceList.size() == 0) {
            return sourceList;
        }
        List random = new ArrayList(sourceList.size());
        do {
            int index = Math.abs(new Random().nextInt(sourceList.size()));
            random.add(sourceList.remove(index));
        } while (sourceList.size() > 0);
        return random;
    }

    public static  List sortList(List sourceList) {
        if (sourceList == null || sourceList.size() == 0) {
            return sourceList;
        }
        List sort = new ArrayList(sourceList.size());
        sort.addAll(sourceList);
        Collections.sort(sort, new Comparator(){
            @Override
            public int compare(V v0, V v1) {
                List list = new ArrayList(2);
                list.add(v0.toString());
                list.add(v1.toString());
                Collections.sort(list, Collator.getInstance(ja va.util.Locale.CHINA));
                return list.indexOf(v0.toString()) == 0 ? -1 : 1;
            }
        });
        return sort;
    }
}

十三. Redis工具类

基于Spring Data Redis封装了一个通用的缓存操作工具，支持String、List、Set、Map等常用数据结构，同时封装了删除方法。使用时需要先配置好Redis连接。

1. properties配置文件

# redis 配置文件
redis.hostName=127.0.0.1
redis.port=6379
redis.timeout=36000
redis.usePool=true 
redis.maxIdle=6
redis.minEvictableIdleTimeMillis=300000
redis.numTestsPerEvictionRun=3
redis.timeBetweenEvictionRunsMillis=60000

2. Spring添加配置文件

3. Ma ven依赖


    org.springframework.data
    spring-data-redis
    1.6.2.RELEASE


    redis.clients
    jedis
    2.9.0

4. Redis工具类

import ja va.util.Iterator;
import ja va.util.List;
import ja va.util.Map;
import ja va.util.Set;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.data.redis.core.BoundListOperations;
import org.springframework.data.redis.core.BoundSetOperations;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Service;

@Service
public class RedisCacheUtil {
    @Autowired
    @Qualifier("jedisTemplate")
    public RedisTemplate redisTemplate;

    public  void setCacheObject(K key, V value) {
        redisTemplate.boundValueOps(key).set(value);
    }

    @SuppressWarnings("unchecked")
    public  V getCacheObject(K key) {
        return (V) redisTemplate.boundValueOps(key).get();
    }

    public  void setCacheList(K key, List dataList) {
        redisTemplate.delete(key);
        for (V v : dataList) {
            redisTemplate.boundListOps(key).rightPush(v);
        }
    }

    @SuppressWarnings("unchecked")
    public  List getCacheList(K key) {
        BoundListOperations listOperation = (BoundListOperations) redisTemplate.boundListOps(key);
        return listOperation.range(0, listOperation.size());
    }

    @SuppressWarnings("unchecked")
    public  void setCacheSet(K key, Set dataSet) {
        redisTemplate.delete(key);
        BoundSetOperations setOperation = (BoundSetOperations) redisTemplate.boundSetOps(key);
        Iterator it = dataSet.iterator();
        while (it.hasNext()) {
            setOperation.add(it.next());
        }
    }

    @SuppressWarnings("unchecked")
    public  Set getCacheSet(K key) {
        return (Set) redisTemplate.boundSetOps(key).members();
    }

    public  void setCacheMap(K key, Map dataMap) {
        redisTemplate.delete(key);
        redisTemplate.boundHashOps(key).putAll(dataMap);
    }

    @SuppressWarnings("unchecked")
    public  Map getCacheMap(K key) {
        return (Map) redisTemplate.boundHashOps(key).entries();
    }

    public  void deleteByKey(K key) {
        redisTemplate.delete(redisTemplate.keys(key));
    }
}

十四. 判断是否是中文

有时候需要检查字符串是否包含中文字符，可以通过Unicode编码范围来判断。下面这个工具类支持中文汉字和中文符号。

public class CharUtils {
    public static boolean isChinese(String strName) {
        char[] ch = strName.toCharArray();
        for (int i = 0; i < ch.length; i++) {
            char c = ch[i];
            if (isChinese(c)) {
                return true;
            }
        }
        return false;
    }

    private static boolean isChinese(char c) {
        Character.UnicodeBlock ub = Character.UnicodeBlock.of(c);
        if (ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS
                || ub == Character.UnicodeBlock.CJK_COMPATIBILITY_IDEOGRAPHS
                || ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS_EXTENSION_A
                || ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS_EXTENSION_B
                || ub == Character.UnicodeBlock.CJK_SYMBOLS_AND_PUNCTUATION
                || ub == Character.UnicodeBlock.HALFWIDTH_AND_FULLWIDTH_FORMS
                || ub == Character.UnicodeBlock.GENERAL_PUNCTUATION) {
            return true;
        }
        return false;
    }
}

十五. 异常拦截处理

全局异常处理器是Spring MVC中非常重要的一环。这里实现了 HandlerExceptionResolver 接口，针对自定义异常、数据库主键重复、Shiro权限不足等分别返回不同的JSON信息，同时记录日志。

import ja vax.servlet.http.HttpServletRequest;
import ja vax.servlet.http.HttpServletResponse;
import org.apache.shiro.authz.AuthorizationException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.dao.DuplicateKeyException;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;
import com.alibaba.fastjson.JSON;

@Component
public class RRExceptionHandler implements HandlerExceptionResolver {
    private Logger logger = LoggerFactory.getLogger(getClass());

    @Override
    public ModelAndView resolveException(HttpServletRequest request,
            HttpServletResponse response, Object handler, Exception ex) {
        R r = new R();
        try {
            response.setContentType("application/json;charset=utf-8");
            response.setCharacterEncoding("utf-8");
            if (ex instanceof RRException) {
                r.put("code", ((RRException) ex).getCode());
                r.put("msg", ((RRException) ex).getMessage());
                r.put("tip", ((RRException) ex).getMessage());
            }
            else if(ex instanceof DuplicateKeyException){
                r = R.error("数据库中已存在该记录");
            }
            else if(ex instanceof AuthorizationException){
                r = R.error("没有权限，请联系管理员授权").put("tip", "没有权限，请联系管理员授权").put("content", null);
            }
            else{
                r = R.error();
            }
            logger.error(ex.getMessage(), ex);
            String json = JSON.toJSONString(r);
            response.getWriter().print(json);
        } catch (Exception e) {
            logger.error("RRExceptionHandler 异常处理失败", e);
            e.printStackTrace();
        }
        return new ModelAndView();
    }
}

十六. Cookie工具类

Cookie操作虽然简单，但涉及到编码、域名、路径等细节。这个工具类提供了获取、设置、删除Cookie的方法，支持编码和解码，同时考虑了多级域名的情况。

import ja va.io.UnsupportedEncodingException;
import ja va.net.URLDecoder;
import ja va.net.URLEncoder;
import ja vax.servlet.http.Cookie;
import ja vax.servlet.http.HttpServletRequest;
import ja vax.servlet.http.HttpServletResponse;

public class CookieUtils {
     public static String getCookieValue(HttpServletRequest request, String cookieName) {
        return getCookieValue(request, cookieName, false);
    }

    public static String getCookieValue(HttpServletRequest request, String cookieName, boolean isDecoder) {
        Cookie[] cookieList = request.getCookies();
        if (cookieList == null || cookieName == null) {
            return null;
        }
        String retValue = null;
        try {
            for (int i = 0; i < cookieList.length; i++) {
                if (cookieList[i].getName().equals(cookieName)) {
                    if (isDecoder) {
                        retValue = URLDecoder.decode(cookieList[i].getValue(), "UTF-8");
                    } else {
                        retValue = cookieList[i].getValue();
                    }
                    break;
                }
            }
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return retValue;
    }

    public static String getCookieValue(HttpServletRequest request, String cookieName, String encodeString) {
        Cookie[] cookieList = request.getCookies();
        if (cookieList == null || cookieName == null) {
            return null;
        }
        String retValue = null;
        try {
            for (int i = 0; i < cookieList.length; i++) {
                if (cookieList[i].getName().equals(cookieName)) {
                    retValue = URLDecoder.decode(cookieList[i].getValue(), encodeString);
                    break;
                }
            }
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return retValue;
    }

    public static void setCookie(HttpServletRequest request, HttpServletResponse response, String cookieName,
            String cookieValue) {
        setCookie(request, response, cookieName, cookieValue, -1);
    }

    public static void setCookie(HttpServletRequest request, HttpServletResponse response, String cookieName,
            String cookieValue, int cookieMaxage) {
        setCookie(request, response, cookieName, cookieValue, cookieMaxage, false);
    }

    public static void setCookie(HttpServletRequest request, HttpServletResponse response, String cookieName,
            String cookieValue, boolean isEncode) {
        setCookie(request, response, cookieName, cookieValue, -1, isEncode);
    }

    public static void setCookie(HttpServletRequest request, HttpServletResponse response, String cookieName,
            String cookieValue, int cookieMaxage, boolean isEncode) {
        doSetCookie(request, response, cookieName, cookieValue, cookieMaxage, isEncode);
    }

    public static void setCookie(HttpServletRequest request, HttpServletResponse response, String cookieName,
            String cookieValue, int cookieMaxage, String encodeString) {
        doSetCookie(request, response, cookieName, cookieValue, cookieMaxage, encodeString);
    }

    public static void deleteCookie(HttpServletRequest request, HttpServletResponse response,
            String cookieName) {
        doSetCookie(request, response, cookieName, "", -1, false);
    }

    private static final void doSetCookie(HttpServletRequest request, HttpServletResponse response,
            String cookieName, String cookieValue, int cookieMaxage, boolean isEncode) {
        try {
            if (cookieValue == null) {
                cookieValue = "";
            } else if (isEncode) {
                cookieValue = URLEncoder.encode(cookieValue, "utf-8");
            }
            Cookie cookie = new Cookie(cookieName, cookieValue);
            if (cookieMaxage > 0)
                cookie.setMaxAge(cookieMaxage);
            if (null != request) {
                String domainName = getDomainName(request);
                System.out.println(domainName);
                if (!"localhost".equals(domainName)) {
                }
            }
            cookie.setPath("/");
            response.addCookie(cookie);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static final void doSetCookie(HttpServletRequest request, HttpServletResponse response,
            String cookieName, String cookieValue, int cookieMaxage, String encodeString) {
        try {
            if (cookieValue == null) {
                cookieValue = "";
            } else {
                cookieValue = URLEncoder.encode(cookieValue, encodeString);
            }
            Cookie cookie = new Cookie(cookieName, cookieValue);
            if (cookieMaxage > 0)
                cookie.setMaxAge(cookieMaxage);
            if (null != request) {
                String domainName = getDomainName(request);
                System.out.println(domainName);
                if (!"localhost".equals(domainName)) {
                }
            }
            cookie.setPath("/");
            response.addCookie(cookie);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static final String getDomainName(HttpServletRequest request) {
        String domainName = null;
        String serverName = request.getRequestURL().toString();
        if (serverName == null || serverName.equals("")) {
            domainName = "";
        } else {
            final int end = serverName.lastIndexOf("/");
            serverName = serverName.substring(0, end);
            final String[] domains = serverName.split("\\.");
            int len = domains.length;
            if (len > 3) {
                domainName = "." + domains[len - 3] + "." + domains[len - 2] + "." + domains[len - 1];
            } else if (len <= 3 && len > 1) {
                domainName = "." + domains[len - 2] + "." + domains[len - 1];
            } else {
                domainName = serverName;
            }
        }
        if (domainName != null && domainName.indexOf(":") > 0) {
            String[] ary = domainName.split(":");
            domainName = ary[0];
        }
        return domainName;
    }
}

十七. 日期处理

日期格式化、获取某月的所有日期、判断是否同一天、计算相差天数——这些是日常开发中很常见的需求。下面这个工具类封装了这些方法，可以直接使用。

import ja va.text.SimpleDateFormat;
import ja va.util.ArrayList;
import ja va.util.Calendar;
import ja va.util.Date;
import ja va.util.List;

public class DateUtils {
    public final static String DATE_PATTERN = "yyyy-MM-dd";
    public final static String DATE_TIME_PATTERN = "yyyy-MM-dd HH:mm:ss";

    public static String format(Date date) {
        return format(date, DATE_PATTERN);
    }

    public static String format(Date date, String pattern) {
        if (date != null) {
            SimpleDateFormat df = new SimpleDateFormat(pattern);
            return df.format(date);
        }
        return null;
    }

    public static List getAllDatesOfMonth(Date date) {
        List list = new ArrayList();
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        cal.set(Calendar.DATE, 1);
        int month = cal.get(Calendar.MONTH);
        while (cal.get(Calendar.MONTH) == month) {
            list.add(cal.getTime());
            cal.add(Calendar.DATE, 1);
        }
        return list;
    }

    public static boolean isSameDate(Date date1, Date date2) {
        Calendar cal1 = Calendar.getInstance();
        cal1.setTime(date1);
        Calendar cal2 = Calendar.getInstance();
        cal2.setTime(date2);
        boolean isSameYear = cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR);
        boolean isSameMonth = isSameYear && cal1.get(Calendar.MONTH) == cal2.get(Calendar.MONTH);
        boolean isSameDate = isSameMonth && cal1.get(Calendar.DAY_OF_MONTH) == cal2.get(Calendar.DAY_OF_MONTH);
        return isSameDate;
    }

    public static int getDateSpace(Date date1, Date date2) {
        Calendar calst = Calendar.getInstance();
        Calendar caled = Calendar.getInstance();
        calst.setTime(date1);
        caled.setTime(date2);
        calst.set(Calendar.HOUR_OF_DAY, 0);
        calst.set(Calendar.MINUTE, 0);
        calst.set(Calendar.SECOND, 0);
        caled.set(Calendar.HOUR_OF_DAY, 0);
        caled.set(Calendar.MINUTE, 0);
        caled.set(Calendar.SECOND, 0);
        return ((int) (caled.getTime().getTime() / 1000) - (int) (calst.getTime().getTime() / 1000)) / 3600 / 24;
    }
}

十八. HttpClient工具类(通过Ja va后台进行Http访问)

Ja va后端经常需要调用其他系统的HTTP接口，Apache HttpClient 是经典选择。这里封装了GET、POST请求（支持参数）、文件上传、文件下载以及SSL连接（支持证书导入和信任所有证书两种方式）。

1. Ma ven导包


    org.apache.httpcomponents
    httpclient
    4.3.1


    org.apache.httpcomponents
    httpcore
    4.3.1


    org.apache.httpcomponents
    httpmime
    4.3.1

2. Ja va代码

import ja va.io.File;
import ja va.io.FileInputStream;
import ja va.io.FileOutputStream;
import ja va.io.IOException;
import ja va.io.InputStream;
import ja va.io.UnsupportedEncodingException;
import ja va.security.KeyManagementException;
import ja va.security.KeyStore;
import ja va.security.KeyStoreException;
import ja va.security.NoSuchAlgorithmException;
import ja va.security.cert.CertificateException;
import ja va.security.cert.X509Certificate;
import ja va.util.ArrayList;
import ja va.util.HashMap;
import ja va.util.List;
import ja va.util.Map;
import ja va.util.Set;
import ja vax.net.ssl.SSLContext;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLContextBuilder;
import org.apache.http.conn.ssl.SSLContexts;
import org.apache.http.conn.ssl.TrustSelfSignedStrategy;
import org.apache.http.conn.ssl.TrustStrategy;
import org.apache.http.entity.mime.HttpMultipartMode;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.FileBody;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicHeader;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.CharsetUtils;
import org.apache.http.util.EntityUtils;

public class HttpClientUtils {
    private static final int SUCCESS = 200;

    public static void ssl(String url) {
        CloseableHttpClient httpclient = null;
        try {
            KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());
            FileInputStream instream = new FileInputStream(new File("E:tomcat.keystore"));
            try {
                trustStore.load(instream, "123456".toCharArray());
            } catch (CertificateException e) {
                e.printStackTrace();
            } finally {
                try {
                    instream.close();
                } catch (Exception ignore) {
                }
            }
            SSLContext sslcontext = SSLContexts.custom()
                    .loadTrustMaterial(trustStore, new TrustSelfSignedStrategy())
                    .build();
            SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(
                    sslcontext, new String[] { "TLSv1" }, null,
                    SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);
            httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build();
            HttpGet httpget = new HttpGet(url);
            System.out.println("executing request" + httpget.getRequestLine());
            CloseableHttpResponse response = httpclient.execute(httpget);
            try {
                HttpEntity entity = response.getEntity();
                System.out.println("----------------------------------------");
                System.out.println(response.getStatusLine());
                if (entity != null) {
                    System.out.println("Response content length: " + entity.getContentLength());
                    System.out.println(EntityUtils.toString(entity));
                    EntityUtils.consume(entity);
                }
            } finally {
                response.close();
            }
        } catch (ParseException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (KeyManagementException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (KeyStoreException e) {
            e.printStackTrace();
        } finally {
            if (httpclient != null) {
                try {
                    httpclient.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static CloseableHttpClient createSSLClientDefault() {
        try {
            SSLContext sslContext = new SSLContextBuilder().loadTrustMaterial(null, new TrustStrategy() {
                public boolean isTrusted(X509Certificate[] chain, String authType) throws CertificateException {
                    return true;
                }
            }).build();
            SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslContext);
            return HttpClients.custom().setSSLSocketFactory(sslsf).build();
        } catch (KeyManagementException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (KeyStoreException e) {
            e.printStackTrace();
        }
        return HttpClients.createDefault();
    }

    public static void ssl2(String url) {
        CloseableHttpClient httpclient = null;
        try {
            httpclient = createSSLClientDefault();
            HttpGet httpget = new HttpGet(url);
            System.out.println("executing request" + httpget.getRequestLine());
            CloseableHttpResponse response = httpclient.execute(httpget);
            try {
                HttpEntity entity = response.getEntity();
                System.out.println("----------------------------------------");
                System.out.println(response.getStatusLine());
                if (entity != null) {
                    System.out.println("Response content length: " + entity.getContentLength());
                    System.out.println(EntityUtils.toString(entity));
                    EntityUtils.consume(entity);
                }
            } finally {
                response.close();
            }
        } catch (ParseException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (httpclient != null) {
                try {
                    httpclient.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    private static void closeClientAndResponse(CloseableHttpClient client, CloseableHttpResponse response) {
        try {
            if (response != null) {
                response.close();
            }
            if (client != null) {
                client.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static Map doGet(String url, Map params) {
        Map result = new HashMap<>(2);
        result.put("code", "200");
        CloseableHttpClient client = null;
        CloseableHttpResponse response = null;
        try {
            client = HttpClients.createDefault();
            URIBuilder uri = new URIBuilder(url);
            if (params != null) {
                Set> entries = params.entrySet();
                for (Map.Entry entry : entries) {
                    uri.addParameter(entry.getKey(), entry.getValue());
                }
            }
            HttpGet hg = new HttpGet(uri.build());
            hg.setHeader(new BasicHeader("Content-Type", "application/x-www-form-urlencoded; charset=utf-8"));
            hg.setHeader(new BasicHeader("Accept", "application/json;charset=utf-8"));
            response = client.execute(hg);
            int statusCode = response.getStatusLine().getStatusCode();
            if (statusCode == SUCCESS) {
                String resStr = EntityUtils.toString(response.getEntity(), "utf-8");
                result.put("data", resStr);
            } else {
                result.put("code", statusCode + "");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            closeClientAndResponse(client, response);
        }
        return result;
    }

    public static Map doPost(String url, Map params){
        Map result = new HashMap<>(2);
        result.put("code", "200");
        CloseableHttpClient client = null;
        CloseableHttpResponse response = null;
        try {
            client = HttpClients.createDefault();
            HttpPost post = new HttpPost(url);
            List formList = new ArrayList<>();
            if (params != null) {
                Set> entries = params.entrySet();
                for (Map.Entry entry : entries) {
                    formList.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
                }
            }
            StringEntity entity = new UrlEncodedFormEntity(formList, "utf-8");
            post.setEntity(entity);
            post.setHeader(new BasicHeader("Content-Type", "application/x-www-form-urlencoded; charset=utf-8"));
            post.setHeader(new BasicHeader("Accept", "application/json;charset=utf-8"));
            response = client.execute(post);
            int statusCode = response.getStatusLine().getStatusCode();
            if (statusCode == SUCCESS) {
                String resStr = EntityUtils.toString(response.getEntity(), "utf-8");
                result.put("data", resStr);
            } else {
                result.put("code", statusCode + "");
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            closeClientAndResponse(client, response);
        }
        return result;
    }

    public static void upload(String url) {
        CloseableHttpClient httpclient = HttpClients.createDefault();
        try {
            HttpPost httppost = new HttpPost(url);
            FileBody bin = new FileBody(new File("C:UserszhangwenchaoDesktopjinzhongzi.jpg"));
            HttpEntity reqEntity = MultipartEntityBuilder.create()
                    .setMode(HttpMultipartMode.BROWSER_COMPATIBLE)
                    .addPart("uploadFile", bin)
                    .setCharset(CharsetUtils.get("UTF-8"))
                    .build();
            httppost.setEntity(reqEntity);
            System.out.println("executing request: " + httppost.getRequestLine());
            CloseableHttpResponse response = httpclient.execute(httppost);
            try {
                System.out.println("----------------------------------------");
                System.out.println(response.getStatusLine());
                HttpEntity resEntity = response.getEntity();
                if (resEntity != null) {
                    System.out.println("Response content length: " + resEntity.getContentLength());
                    System.out.println("Response content: " + EntityUtils.toString(resEntity));
                }
                EntityUtils.consume(resEntity);
            } finally {
                response.close();
            }
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                httpclient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static void download(String url) {
        CloseableHttpClient httpclient = HttpClients.createDefault();
        try {
            HttpGet httpget = new HttpGet(url);
            CloseableHttpResponse response = httpclient.execute(httpget);
            HttpEntity resEntity = response.getEntity();
            if (resEntity != null) {
                System.out.println("Response content length: " + resEntity.getContentLength());
                InputStream in = resEntity.getContent();
                String fileName = url.substring(url.lastIndexOf("/"));
                File file = new File("E:" + fileName);
                try {
                    FileOutputStream fout = new FileOutputStream(file);
                    int l = -1;
                    byte[] tmp = new byte[1024];
                    while ((l = in.read(tmp)) != -1) {
                        fout.write(tmp, 0, l);
                    }
                    fout.flush();
                    fout.close();
                } finally {
                    in.close();
                }
            }
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                httpclient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

十九. 分页工具类

分页是后台系统的标配。这个 PageUtils 封装了总记录数、每页大小、总页数、当前页和分页数据，使用起来很直观。

import ja va.io.Serializable;
import ja va.util.List;

public class PageUtils implements Serializable {
    private static final long serialVersionUID = 1L;
    private int totalCount;
    private int pageSize;
    private int totalPage;
    private int currPage;
    private List list;

    public PageUtils(List list, int totalCount, int pageSize, int currPage) {
        this.list = list;
        this.totalCount = totalCount;
        this.pageSize = pageSize;
        this.currPage = currPage;
        this.totalPage = (int)Math.ceil((double)totalCount/pageSize);
    }

    // getters and setters omitted for brevity
}

二十. SQL查询工具类

在MyBatis中动态拼SQL时，排序字段容易产生SQL注入风险。下面这个工具类包含SQL过滤和查询参数封装，避免直接拼接。

1. SQL过滤

import org.apache.commons.lang.StringUtils;

public class SQLFilter {
    public static String sqlInject(String str){
        if(StringUtils.isBlank(str)){
            return str;
        }
        str = StringUtils.replace(str, "'", "");
        str = StringUtils.replace(str, "\"", "");
        str = StringUtils.replace(str, ";", "");
        str = StringUtils.replace(str, "\\", "");
        str = str.toLowerCase();
        String[] keywords = {"master", "truncate", "insert", "select", "delete", "update", "declare", "alert", "drop"};
        for(String keyword : keywords){
            if(str.contains(keyword)){
                throw new RuntimeException("包含非法字符");
            }
        }
        return str;
    }
}

2. SQL查询

import ja va.util.LinkedHashMap;
import ja va.util.Map;

public class Q extends LinkedHashMap {
    private static final long serialVersionUID = 1L;
    private int page;
    private int limit;

    public Q(Map params){
        this.putAll(params);
        String sidx = "";
        String order = "";
        if(params.get("page")!=null) {
            this.page = Integer.parseInt(params.get("page").toString());
        }
        if(params.get("limit")!=null) {
            this.limit = Integer.parseInt(params.get("limit").toString());
        }
        if(params.get("sidx")!=null) {
            sidx = params.get("sidx").toString();
        }
        if(params.get("order")!=null) {
            order = params.get("order").toString();
        }
        this.put("offset", (page - 1) * limit);
        this.put("page", page);
        this.put("limit", limit);
        if(params.get("limit")==null) {
            this.put("limit", null);
        }
        this.put("sidx", SQLFilter.sqlInject(sidx));
        this.put("order", SQLFilter.sqlInject(order));
    }

    public Q() {
        this.put("page", page);
        this.put("limit", null);
        this.put("sidx", "");
        this.put("order", "");
    }

    // getters and setters omitted
}

3. mapper文件中查询列表可以这么写

二十一. Shiro工具类

Apache Shiro 是Ja va常见的权限框架。下面这个工具类封装了获取Session、Subject、当前用户信息、验证码等常见操作。

1. Ma ven导包


    org.apache.shiro
    shiro-core
    1.3.2


    org.apache.shiro
    shiro-spring
    1.3.2


    org.apache.shiro
    shiro-ehcache
    1.3.2

2. 工具类

import org.apache.shiro.SecurityUtils;
import org.apache.shiro.session.Session;
import org.apache.shiro.subject.Subject;

public class ShiroUtils {
    public static Session getSession() {
        return SecurityUtils.getSubject().getSession();
    }

    public static Subject getSubject() {
        return SecurityUtils.getSubject();
    }

    public static SysUserEntity getUserEntity() {
        return (SysUserEntity)SecurityUtils.getSubject().getPrincipal();
    }

    public static Long getUserId() {
        return getUserEntity().getUserId();
    }

    public static void setSessionAttribute(Object key, Object value) {
        getSession().setAttribute(key, value);
    }

    public static Object getSessionAttribute(Object key) {
        return getSession().getAttribute(key);
    }

    public static boolean isLogin() {
        return SecurityUtils.getSubject().getPrincipal() != null;
    }

    public static void logout() {
        SecurityUtils.getSubject().logout();
    }

    public static String getKaptcha(String key) {
        String kaptcha = getSessionAttribute(key).toString();
        getSession().removeAttribute(key);
        return kaptcha;
    }
}

二十二. SpringContext工具类

有时候我们需要在非Spring管理的类中获取Bean，实现 ApplicationContextAware 接口是最常用的方式。工具类如下：

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

@Component
public class SpringContextUtils implements ApplicationContextAware {
    public static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext)
            throws BeansException {
        SpringContextUtils.applicationContext = applicationContext;
    }

    public static Object getBean(String name) {
        return applicationContext.getBean(name);
    }

    public static  T getBean(String name, Class requiredType) {
        return applicationContext.getBean(name, requiredType);
    }

    public static boolean containsBean(String name) {
        return applicationContext.containsBean(name);
    }

    public static boolean isSingleton(String name) {
        return applicationContext.isSingleton(name);
    }

    public static Class getType(String name) {
        return applicationContext.getType(name);
    }
}

二十三. Properties载入工具类

读取properties配置文件时，这个工具类可以指定多个文件，并支持UTF-8编码，避免中文乱码。

1. 工具类如下

import ja va.io.IOException;
import ja va.io.InputStreamReader;
import ja va.util.Properties;

public class PropertiesLoader {
    private final Properties properties;

    public PropertiesLoader(String... resourcePaths) {
        properties = loadProperties(resourcePaths);
    }

    private Properties loadProperties(String[] resourcePaths) {
        Properties props = new Properties();
        for (String location : resourcePaths) {
            InputStreamReader is = null;
            try {
                is = new InputStreamReader(
                        PropertiesLoader.class.getClassLoader().getResourceAsStream(location), "UTF-8");
                props.load(is);
            } catch (Exception e) {
            } finally {
                try {
                    is.close();
                } catch (IOException e) {
                }
            }
        }
        return props;
    }

    public String getConfig(String key) {
        if (properties.containsKey(key)) {
            return properties.getProperty(key);
        }
        return "";
    }

    public int getIntConfig(String key) {
        return Integer.parseInt(getConfig(key));
    }
}

2. 使用

public static PropertiesLoader loader = new PropertiesLoader("config/config.properties");
public void test() {
    String content = loader.getConfig("content");
}

二十四. Ja va执行Bat命令(或其他命令)

有时候需要从Ja va调用外部脚本（比如批处理）。下面这个工具类通过 ProcessBuilder 执行bat文件，并通过判断输出中的特定标记来确认执行结果。

import ja va.io.BufferedReader;
import ja va.io.IOException;
import ja va.io.InputStreamReader;
import ja va.nio.charset.StandardCharsets;

public class BatUtils {
    public static boolean doBat(String batPath, String... args) {
        boolean result = false;
        String[] command;
        if (args == null || args.length == 0) {
            command = new String[]{batPath};
        } else {
            command = new String[args.length + 1];
            command[0] = batPath;
            System.arraycopy(args, 0, command, 1, args.length);
        }
        ProcessBuilder processBuilder = new ProcessBuilder(command);
        processBuilder.redirectErrorStream(true);
        try {
            Process process = processBuilder.start();
            BufferedReader bufferedReader = new BufferedReader(
                    new InputStreamReader(process.getInputStream(), StandardCharsets.UTF_8));
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                System.out.println(line);
                if (line.contains("Bat Finished! ")) {
                    line = bufferedReader.readLine();
                    System.out.println(line);
                    if (line.contains("Bat Success! ")) {
                        result = true;
                    } else if (line.contains("Bat Fail! ")){
                        // result remains false
                    }
                    break;
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }
}

二十五. 不使用Request获得Web项目的全路径

在非Web环境下（比如工具类中）获取class文件的绝对路径，可以用 getResource("").getFile()。注意返回的路径前后都带有斜杠。

String path = Test.class.getResource("").getFile();

假如Test.class类文件在blog项目的 com/paulandcode/utils 目录下，则上面的path值为：

/D:/Tomcat/webapps/blog/WEB-INF/classes/com/paulandcode/utils/

二十六. 下划线与驼峰相互转换

数据库字段通常采用下划线命名（如 user_name），而Ja va实体类则使用驼峰（如 userName）。这个工具类支持数组和Map的键转换。

import ja va.util.HashMap;
import ja va.util.Map;

public class HumpUtils {
    private static final char UNDERLINE = '_';

    public static String[] arrUnderlineToHump(String[] arr) {
        if (arr == null) return null;
        String[] newArr = new String[arr.length];
        for (int i = 0; i < arr.length; i++) {
            newArr[i] = toHump(arr[i]);
        }
        return newArr;
    }

    public static String[] arrHumpToUnderline(String[] arr) {
        if (arr == null) return null;
        String[] newArr = new String[arr.length];
        for (int i = 0; i < arr.length; i++) {
            newArr[i] = toUnderline(arr[i]);
        }
        return newArr;
    }

    public static  Map mapKeyUnderlineToHump(Map map) {
        if (map == null) return null;
        Map newMap = new HashMap<>(map.size());
        for (Map.Entry entry : map.entrySet()) {
            newMap.put(toHump(entry.getKey()), entry.getValue());
        }
        return newMap;
    }

    public static  Map mapKeyHumpToUnderline(Map map) {
        if (map == null) return null;
        Map newMap = new HashMap<>(map.size());
        for (Map.Entry entry : map.entrySet()) {
            newMap.put(toUnderline(entry.getKey()), entry.getValue());
        }
        return newMap;
    }

    public static String toHump(String colName) {
        if (colName == null) return null;
        StringBuilder sb = new

一. JDK环境变量配置

1. 位置

2. 作用域

3. 配置内容

二. Ja va后台获得客户端IP

三. 无参获取Request和Response

四. Ja va代码行数统计

五. 判断设备类型(PC, 手机等), 浏览器类型(IE, Google等)

1. Ma ven导包如下

2. 工具类如下

3. 进行拦截并根据需要进行处理

六. 根据日期生成目录

七. 根据附件名获得附件类型

1. Ma ven导包

2. 工具类

八. 附件上传下载

1. web.xml中需要加入如下代码

2. Ja va代码如下

九. 获得UUID

十. 自定义异常类

十一. 字符串首字母大写

十二. List乱序与按照汉字拼音排序

十三. Redis工具类

1. properties配置文件

2. Spring添加配置文件

3. Ma ven依赖

4. Redis工具类

十四. 判断是否是中文

十五. 异常拦截处理

十六. Cookie工具类

十七. 日期处理

十八. HttpClient工具类(通过Ja va后台进行Http访问)

1. Ma ven导包

2. Ja va代码

十九. 分页工具类

二十. SQL查询工具类

1. SQL过滤

2. SQL查询

3. mapper文件中查询列表可以这么写

二十一. Shiro工具类

1. Ma ven导包

2. 工具类

二十二. SpringContext工具类

二十三. Properties载入工具类

1. 工具类如下

2. 使用

二十四. Ja va执行Bat命令(或其他命令)

二十五. 不使用Request获得Web项目的全路径

二十六. 下划线与驼峰相互转换

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