Filter案例（字符过滤器）

两种情况都需要配置web.xml
如果是tomcat服务其为8.0版本的字符过滤其如下所示
1.
package com.rupeng.web;

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 {
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
//对请求的编码做处理
//如果使用的是tomcat服务器，所以只需要对post请求时的请求体数据进行编码处理
request.setCharacterEncoding(“utf-8”);//tomcat会对查询字符串自动进行处理
//如果是post请求，上面的代码就起作用，如果是get请求，上面的字符串不起作用，但是没关系

    //顺便对响应的编码也做一下处理   response.setCharacterEncoding("utf-8");    System.out.println("字符编码过滤器执行了");    chain.doFilter(request, response);}public void init(FilterConfig fConfig) throws ServletException {}

}

2 如果是tomcat服务其不是8.0版本的字符过滤其如下所示/

/如果是不是tomocat版本8的处理其，如何设置字符过滤器
//如下所示，当然也同时兼容tomocat版本8的服务器
package com.rupeng.web;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class CharacterEncodingFilter2 implements Filter {

private int mainVersion;public void init(FilterConfig filterConfig) throws ServletException {    // 获取服务器信息，判断是不是Tomcat8以上的版本    String serverInfo = filterConfig.getServletContext().getServerInfo();//获取到服务器的信息    // 两种版本的serverInfo示例：Apache Tomcat/7.0.69 、Apache Tomcat/8.0.36    if (serverInfo.startsWith("Apache Tomcat")) {        // 获取主版本        mainVersion = Integer.parseInt(serverInfo.substring(14, 15));    }}public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)        throws IOException, ServletException {    if (mainVersion >= 8) {        // 处理请求体中数据的编码（查询字符串已经）        request.setCharacterEncoding("UTF-8");        // 也顺便对响应编码进行处理        response.setCharacterEncoding("UTF-8");        chain.doFilter(request, response);    } else {        HttpServletRequest httpRequest = (HttpServletRequest) request;        // 使用自己的request对象包装原request对象，实现对请求参数编码处理的效果        MyHttpServletRequest myRequest = new MyHttpServletRequest(httpRequest);        // 也顺便对响应编码进行处理        response.setCharacterEncoding("UTF-8");        chain.doFilter(myRequest, response);    }}public void destroy() {}

}
// 自己包装的request对象，保证所有的获取参数操作都会进行编码处理
class MyHttpServletRequest extends HttpServletRequestWrapper {

public MyHttpServletRequest(HttpServletRequest request) {    super(request);}@Overridepublic String getParameter(String name) {    String value = super.getParameter(name);    value = convertToUtf_8(value);    return value;}private String convertToUtf_8(String oldValue) {    if (oldValue != null && oldValue.length() > 0) {        try {            oldValue = new String(oldValue.getBytes("ISO-8859-1"), "UTF-8");        } catch (UnsupportedEncodingException e) {            throw new RuntimeException(e);        }    }    return oldValue;}private String[] convertToUtf_8(String[] values) {    if (values == null || values.length == 0) {        return values;    }    String[] newValues = new String[values.length];    for (int i = 0; i < values.length; i++) {        newValues[i] = convertToUtf_8(values[i]);    }    return newValues;}// Map<String,String[]>@Overridepublic Map getParameterMap() {    Map<String, String[]> map = super.getParameterMap();    Map<String, String[]> newMap = new HashMap<String, String[]>();    for (Entry<String, String[]> entry : map.entrySet()) {        newMap.put(convertToUtf_8(entry.getKey()), convertToUtf_8(entry.getValue()));    }    return newMap;}@Overridepublic String[] getParameterValues(String name) {    return convertToUtf_8(super.getParameterValues(name));}@Overridepublic Enumeration getParameterNames() {    final Enumeration oldEnum = super.getParameterNames();    Enumeration<String> newEnum = new Enumeration<String>() {        public String nextElement() {            return convertToUtf_8((String) oldEnum.nextElement());        }        public boolean hasMoreElements() {            return oldEnum.hasMoreElements();        }    };    return newEnum;}

}
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