使用过滤器对所有请求进行字符编码过滤

过滤器Filter

A filter is an object that performs filtering tasks on either the request to a resource (a servlet or static content), or on the response from a resource, or both.

过滤器对访问资源的请求或服务器的响应进行过滤

Filters perform filtering in the doFilter method.

在doFilter()方法中进行过滤

Filters are configured in the deployment descriptor of a web application

过滤器必须在配置文件web.xml中进行配置

字符过滤器的代码实现

import java.io.IOException;import java.io.UnsupportedEncodingException;import java.util.Enumeration;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;public class CharacterEncodingFilter implements Filter{    protected String encoding = null;    protected FilterConfig filterConfig = null;    protected boolean ignore = true;  //是否忽视指定的字符集 默认为true    @Override    public void destroy() {        this.encoding = null;        this.filterConfig = null;    }    void encoding(HttpServletRequest request){        Enumeration<?> names = request.getParameterNames();        while(names.hasMoreElements()){            String[] values = request.getParameterValues(names.nextElement().toString());            for(int i = 0; i < values.length; i++){                try {                    values[i] = new String(values[i].getBytes("iso-8859-1"),encoding);                } catch (UnsupportedEncodingException e) {                    e.printStackTrace();                }            }        }    }    @Override    public void doFilter(ServletRequest request, ServletResponse response,            FilterChain chain) throws IOException, ServletException {        if(ignore || (request.getCharacterEncoding() == null)){            String encoding = selectEncoding(request);            if(encoding != null){                request.setCharacterEncoding(encoding);            }            HttpServletRequest req = (HttpServletRequest) request;            if(req.getMethod().equalsIgnoreCase("get")){                encoding(req);            }        }        chain.doFilter(request, response);    }    private String selectEncoding(ServletRequest request) {        return (this.encoding);    }    @Override    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;    }}

配置

<filter>    <filter-name>CharacterEncodingFilter</filter-name>    <filter-class>com.icss.filter.CharacterEncodingFilter</filter-class>    <init-param>        <param-name>encoding</param-name>        <param-value>UTF-8</param-value>    </init-param>  </filter>  <filter-mapping>    <filter-name>CharacterEncodingFilter</filter-name>    <url-pattern>/*</url-pattern> <!-- 对所有请求进行过滤 -->  </filter-mapping>