过滤器

<filter>
    <filter-name>setCharacterEncodingFilter</filter-name>
    <filter-class>tools.SetCharacterEncodingFilter</filter-class>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>setCharacterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

 

package tools;

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 SetCharacterEncodingFilter implements Filter ...{
    
    protected String encoding = null;
    
    protected FilterConfig filterConfig = null;
    
    protected boolean ignore = true;

    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;
        }

    }
    //过滤的方法是在这里实现的
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException ...{
        if(ignore || request.getCharacterEncoding()==null)...{//如果忽略编码格式或者制定编码格式为空则从request中获得编码格式
            encoding = selectEncoding(request);            
        }
        if(encoding != null)...{
            request.setCharacterEncoding(this.encoding);
        }
        chain.doFilter(request , response);
    }

    private String selectEncoding(ServletRequest request) ...{ 
        return this.encoding;
    }
    
    public void destroy() ...{
        this.encoding = null;
        this.filterConfig = null;

    }

}