Filter解决全局的编码

步骤：

编写一个过滤器的类实现Filter接口
实现接口中尚未实现的方法(着重实现doFilter方法)
在web.xml中进行配置(主要是配置要对哪些资源进行过滤)

EncidingFilter.java

package web.filter;

import java.io.IOException;
import java.io.UnsupportedEncodingException;

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 EncodingFilter implements Filter{

	
	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
			throws IOException, ServletException {
		
		
		
		//在传递request之前对request的getParameter方法进行增强
		/*
		 * 装饰者模式(包装)
		 * 
		 * 1、增强类与被增强的类要实现统一接口
		 * 2、在增强类中传入被增强的类
		 * 3、需要增强的方法重写 不需要增强的方法调用被增强对象的
		 * 
		 */
		
		//被增强的对象
		HttpServletRequest req = (HttpServletRequest) request;
		//增强对象
		EnhanceRequest enhanceRequest = new EnhanceRequest(req);
		
		
		chain.doFilter(enhanceRequest, response);
		
	}

	@Override
	public void destroy() {
		
	}
	
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		
	}

}

class EnhanceRequest extends HttpServletRequestWrapper{
	
	private HttpServletRequest request;

	public EnhanceRequest(HttpServletRequest request) {
		super(request);
		this.request = request;
	}
	
	//对getParaameter增强
	@Override
	public String getParameter(String name) {
		String parameter = request.getParameter(name);//乱码
		System.out.println(parameter);
		try {
			
			parameter = new String(parameter.getBytes("iso8859-1"),"UTF-8");
			System.out.println("进行编码:"+parameter);
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
		return parameter;
	}
	
}

web.xml中加入这个

  <filter>
    <filter-name>EncodingFilter</filter-name>
    <filter-class>web.filter.EncodingFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>EncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

经过这个Filter的getparameter方法拿到的都是编码过的，想用其他方法，直接增强就行

Filter解决全局的编码

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