002——Filter解决乱码问题

字符编码Filter是最常用的Filter之一，常用来解决Tomcat等服务器里request，response乱码的问题。字符编码Filter是在request提交到Servlet之前对request进行制定编码方式的编码，代码如下：

package com.java.filter;

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;

public class CharacterEncodingFilter implements Filter {

//编码方式，配置在web.xml中
private String characterEncoding;
//是否启用该Filter，配置在web.xml中
private boolean enabled;

public void destroy() {
//销毁时清空资源
characterEncoding = null;
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
//如果启用该filter
if(enabled || characterEncoding != null) {
//设置request编码
request.setCharacterEncoding(characterEncoding);
//设置response编码
response.setCharacterEncoding(characterEncoding);
}
chain.doFilter(request, response);
}
/**
* 初始化时加载参数
*/
public void init(FilterConfig config) throws ServletException {
//编码方式
characterEncoding = config.getInitParameter("characterEncoding");
//启用
enabled = "true".equalsIgnoreCase(config.getInitParameter("enabled").trim());
}

}

characterEncoding表示编码方式，enabled表示是否启用编码，分别从初始化参数中取得。web.xml中的配置代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
<display-name></display-name>

<filter>
<filter-name>characterEncodingFilter</filter-name>
<filter-class>com.java.filter.CharacterEncodingFilter</filter-class>
<init-param>
<param-name>characterEncoding</param-name>
<param-value>utf-8</param-value>
</init-param>
<init-param>
<param-name>enabled</param-name>
<param-value>true</param-value>
</init-param>
</filter>

<filter-mapping>
<filter-name>characterEncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

注意：页面编码方式与Filter编码方式必须一致。另外，如果表单时get方式提交的，还需要修改Tomcat的/conf/server.xml配置文件，指定、URIEncoding(默认为ISO-8859-1);

否则，依然会乱码。修改如下：

<Connector port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443"
URIEncoding="utf-8"/>