使用过滤器对所有请求进行字符编码过滤

た入场券 2022-06-07 12:14 190阅读 0赞

\#\#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> 
      </filter-mapping>