java修改request的paramMap

偏执的太偏执、 2022-08-27 04:56 69阅读 0赞

最近做项目，发现要修改request的参数内容。因为想要在request的paramMap里面默认注入,modifier和modifierName,这些内容。但是这个Map是不能修改的。所以采用了如下办法：下面的办法网上也有的这里只做备份。

1. 创建request转换器

package com.tmall.lafite.web.base;
    
    import java.util.Enumeration;
    import java.util.Map;
    import java.util.Vector;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletRequestWrapper;
    class ParameterRequestWrapper extends HttpServletRequestWrapper {
    
    	private Map<String, String[]> params;
    
    	public ParameterRequestWrapper(HttpServletRequest request,
    			Map<String, String[]> newParams) {
    		super(request);
    		
    		this.params = newParams;
    
    		// RequestDispatcher.forward parameter
    		renewParameterMap(request);
    	}
    
    	@Override
    	public String getParameter(String name) {
    		String result = "";
    		
    		Object v = params.get(name);
    		if (v == null) {
    			result = null;
    		} else if (v instanceof String[]) {
    			String[] strArr = (String[]) v;
    			if (strArr.length > 0) {
    				result =  strArr[0];
    			} else {
    				result = null;
    			}
    		} else if (v instanceof String) {
    			result = (String) v;
    		} else {
    			result =  v.toString();
    		}
    		
    		return result;
    	}
    
    	@Override
    	public Map<String, String[]> getParameterMap() {
    		return params;
    	}
    
    	@Override
    	public Enumeration<String> getParameterNames() {
    		return new Vector<String>(params.keySet()).elements();
    	}
    
    	@Override
    	public String[] getParameterValues(String name) {
    		String[] result = null;
    		
    		Object v = params.get(name);
    		if (v == null) {
    			result =  null;
    		} else if (v instanceof String[]) {
    			result =  (String[]) v;
    		} else if (v instanceof String) {
    			result =  new String[] { (String) v };
    		} else {
    			result =  new String[] { v.toString() };
    		}
    		
    		return result;
    	}
    
    	private void renewParameterMap(HttpServletRequest req) {
    
    		String queryString = req.getQueryString();
    
    		if (queryString != null && queryString.trim().length() > 0) {
    			String[] params = queryString.split("&");
    
    			for (int i = 0; i < params.length; i++) {
    				int splitIndex = params[i].indexOf("=");
    				if (splitIndex == -1) {
    					continue;
    				}
    				
    				String key = params[i].substring(0, splitIndex);
    
    				if (!this.params.containsKey(key)) {
    					if (splitIndex < params[i].length()) {
    						String value = params[i].substring(splitIndex + 1);
    						this.params.put(key, new String[] { value });
    					}
    				}
    			}
    		}
    	}
    
    }

2. 转换filter

package com.tmall.lafite.web.base;
    
    import java.io.IOException;
    import java.util.HashMap;
    import java.util.Map;
    
    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 ParamFilter implements Filter{
    
    	@Override
    	public void init(FilterConfig filterConfig) throws ServletException {
    		// TODO Auto-generated method stub
    		
    	}
    
    	@Override
    	public void doFilter(ServletRequest request, ServletResponse response,
    			FilterChain chain) throws IOException, ServletException {
    		Map<String,String[]> m = new HashMap<String,String[]>(request.getParameterMap());  
    		request = new ParameterRequestWrapper((HttpServletRequest)request, m);  
    		  
    		chain.doFilter(request, response); 
    	}
    
    	@Override
    	public void destroy() {
    		// TODO Auto-generated method stub
    		
    	}
    
    }

3. web.xml

<filter>
    		<filter-name>ParameterFilter</filter-name>
    		<filter-class>com.tmall.lafite.web.base.ParamFilter</filter-class>
    	</filter>
    	<filter-mapping>  
    	    <filter-name>ParameterFilter</filter-name>  
    	    <url-pattern>/*</url-pattern>  
    	    <dispatcher>REQUEST</dispatcher>  
    	    <dispatcher>FORWARD</dispatcher>  
    	</filter-mapping>