Filter解决全局的编码

叁歲伎倆 2022-04-04 05:28 181阅读 0赞

步骤：

1.  编写一个过滤器的类实现Filter接口
2.  实现接口中尚未实现的方法(着重实现doFilter方法)
3.  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