Java 的乱码解决方法 统一编码UTF-8

一、介绍两个类
URLEncoder//编码
URLDecoder//解码

看看下面的测试输出，你就明白是做什么的了

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.net.URLEncoder;

public class main {

public static void main(String[] args) throws UnsupportedEncodingException{
System.out.println("UTF-8");
String a = URLEncoder.encode("中文测试", "UTF-8");//编码
System.out.println(a);
System.out.println(URLDecoder.decode(a,"UTF-8"));//还原
//下面同理
System.out.println("/nGBK(百度就是用这种)");
a = URLEncoder.encode("中文测试", "GBK");
System.out.println(a);
System.out.println(URLDecoder.decode(a,"GBK"));
}
}

[输出]
UTF-8
%E4%B8%AD%E6%96%87%E6%B5%8B%E8%AF%95
中文测试
GBK(百度就是用这种)
%D6%D0%CE%C4%B2%E2%CA%D4
中文测试

看了上面的输出就明白百度地址栏那一串是什么了。假如你做了下面一系列设置，那么在服务器端你接收到Get方法的中文参数将被转换成类型%D6%D0%CE%C4%B2%E2%CA%D4 你就需要用到上面的两个工具类, 如果你像我在下面设置，你在上面的调用的第二个参数也得是UTF-8; 使用post就不需要解码,直接读取就行了。

二、配置tomcat (这一步我没有做，但没发现问题，我用的是Tomcat 5.08经典版本)
打开tomcat的server.xml文件，找到区块，加入如下一行：
URIEncoding="UTF-8"
完整的应如下：
<Connector port="8080" maxThreads="150" minSpareThreads="25" maxSpareThreads="75" enableLookups="false" redirectPort="8443" acceptCount="100" debug="0" connectionTimeout="20000" disableUploadTimeout="true" URIEncoding="UTF-8"/>

三、增加连接数据库的参数
mysql 数据库建表时设置编码为utf8(写法不同不是UTF-8),

连接数据库:
// 连接参数，这里设置连接使用的编码
public static final String DB_URL = "jdbc:mysql://localhost:3306/?useUnicode=true&characterEncoding=utf8";

四、使用过滤器设置编码
1、
// 简单的就用下面这个，这里使用的是硬编码也就是在代码中写死了用那种编码我这里用utf-8，也可以把编码设置用写到web.xml中的Filter设置中
package com.max;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
* Example filter that sets the character encoding to be used in parsing the
* incoming request
*/
public class SetCharacterEncodingFilter implements Filter {

/**
* Take this filter out of service.
*/
public void destroy() {
}
/**
* Select and set (if specified) the character encoding to be used to
* interpret request parameters for this request.
*/
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)throws IOException, ServletException {

request.setCharacterEncoding("UTF-8");

// 传递控制到下一个过滤器
chain.doFilter(request, response);
}

public void init(FilterConfig filterConfig) throws ServletException {
}
}

web.xml配置文件中增加
<filter>
<filter-name>Set Character Encoding</filter-name>
<filter-class>com.max.SetCharacterEncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>Set Character Encoding</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

2、
//下面这个是将编码设置放到web.xml中的

filter类的内容：

/*
* ====================================================================
*
* JavaWebStudio 开源项目
*
* Struts_db v0.1
*
* ====================================================================
*/
package com.strutsLogin.util;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
* 中文过滤器
*/
public class SetCharacterEncodingFilter implements Filter {

// ----------------------------------------------------- Instance Variables

/**
* The default character encoding to set for requests that pass through this
* filter.
*/
protected String encoding = null;

/**
* The filter configuration object we are associated with. If this value is
* null, this filter instance is not currently configured.
*/
protected FilterConfig filterConfig = null;

/**
* Should a character encoding specified by the client be ignored?
*/
protected boolean ignore = true;

// --------------------------------------------------------- Public Methods

/**
* Take this filter out of service.
*/
public void destroy() {

this.encoding = null;
this.filterConfig = null;

}

/**
* Select and set (if specified) the character encoding to be used to
* interpret request parameters for this request.
*
* @param request
* The servlet request we are processing
* @param result
* The servlet response we are creating
* @param chain
* The filter chain we are processing
*
* @exception IOException
* if an input/output error occurs
* @exception ServletException
* if a servlet error occurs
*/
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {

// Conditionally select and set the character encoding to be used
if (ignore || (request.getCharacterEncoding() == null)) {
String encoding = selectEncoding(request);
if (encoding != null)
request.setCharacterEncoding(encoding);
}

// Pass control on to the next filter
chain.doFilter(request, response);

}

/**
* Place this filter into service.
*
* @param filterConfig
* The filter configuration object
*/
public void init(FilterConfig filterConfig) throws ServletException {

this.filterConfig = filterConfig;
this.encoding = filterConfig.getInitParameter("encoding");
String value = filterConfig.getInitParameter("ignore");
if (value == null)
this.ignore = true;
else if (value.equalsIgnoreCase("true"))
this.ignore = true;
else if (value.equalsIgnoreCase("yes"))
this.ignore = true;
else
this.ignore = false;

}

// ------------------------------------------------------ Protected Methods

/**
* Select an appropriate character encoding to be used, based on the
* characteristics of the current request and/or filter initialization
* parameters. If no character encoding should be set, return
* <code>null</code>.
* <p>
* The default implementation unconditionally returns the value configured
* by the <strong>encoding</strong> initialization parameter for this
* filter.
*
* @param request
* The servlet request we are processing
*/
protected String selectEncoding(ServletRequest request) {

return (this.encoding);

}

}// EOC

然后我们在web.xml中加一些配置，就可以了，配置如下：

<filter>
<filter-name>Set Character Encoding</filter-name>
<filter-class>javawebstudio.struts_db.SetCharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
<init-param>
<param-name>ignore</param-name>
<param-value>true</param-value>
</init-param>
</filter>

<filter-mapping>
<filter-name>Set Character Encoding</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

放在web.xml的合适位置。一般在最后，<jsp-config>标签之前(如果有的话)

五、在JSP页面中设置编码

<%@ page language="java" pageEncoding="UTF-8"%>

六、使用i18n
使ApplicationResources.properties支持中文
建立一个ApplicationResources_ISO.properties文件，把应用程序用的message都写进去，然后在dos下执行这个命令，
native2ascii -encoding gb2312 ApplicationResources_ISO.properties ApplicationResources.properties
native2ascii [参数] [输入文件] [输出文件]

native2ascii这个工具是jdk自带的一个东东，所以如果path都设定正确就可以直接运行了，你可以在$java_home$/bin下找到他。
转换后的中文类似于这个样子
中文格式下 ：user_name_label=用户名：
ascii格式下 ：user_name_label=/u7528/u6237/u540D/uFF1A

Netbean 有个方便的编辑多国语言的工具，但不是直接写，而是在弹出窗口中编辑，确定插入后自动转换成ascii如上面那种.
Eclipse 有个一样功能的插件jinto在下面的地址中下载
http://www.guh-software.de/jinto.html

在Jsp页面使用 "user_name_label" 来引用 "用户名：",而且能够简单方便实现多语言支持。

通常将编码同一成UTF-8是很有好处的，如果想使用其他编码如GBK,这上面用到UTF-8全改为GBK