application/json请求如何以form表单形式获取参数

最近工作上,需要对网关进行一下改造。之前网关只支持form表单的提交请求。这里我将如何将只支持form表单请求的网关改造成支持application/json请求，毕竟application/json这种请求使用的很多。

form表单请求,在servlet中使用request.getParameter()获取参数。但是默认通过application/json请求提交，使用这种方式是获取不到参数。只能通过request.getInputStream()读流的形式才获取整个提交的内容。并且在读取之后，无法只重新读取里面的内容。

如果可以让application/json像form表单一样可以通过getParameter(), 这样我们的网关可以不用改写旧的代码。其实很简单，只需要我们将流读取出来的数据转换为JSON对象，并重写getParameter()方法， 并且在HttpFilter过滤器注入我们写的这个request，这样我们自己就实现了一个像form表单一样的request了。嘻嘻， 其实通过这个例子。你就指定springmvc是如何支持application/json转换为实体类的了。相关代码如下:

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.util.Enumeration;
 
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
 
public class BodyReaderHttpServletRequestWrapper extends
		HttpServletRequestWrapper {
	
	private final byte[] body;
    private JSONObject requestParameter;
    public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
        super(request);
        System.out.println("-------------------------------------------------");  
        Enumeration e = request.getHeaderNames()   ;  
         while(e.hasMoreElements()){  
             String name = (String) e.nextElement();  
             String value = request.getHeader(name);  
             System.out.println(name+" = "+value);  
               
         }  
        body = getBodyString(request).getBytes(Charset.forName("UTF-8"));
    	requestParametere = JSON.parseObject(getBodyString(request));
    }
 
    @Override
    public BufferedReader getReader() throws IOException {
        return new BufferedReader(new InputStreamReader(getInputStream()));
    }
    // 重写getParameter方法， 使它可以像form表单一样获取参数
    @Override 
    public String getParameter(String key){
	   return requestParameter.getString(key);
   }
    @Override
    public ServletInputStream getInputStream() throws IOException {
 
        final ByteArrayInputStream bais = new ByteArrayInputStream(body);
 
        return new ServletInputStream() {
            @Override
            public int read() throws IOException {
                return bais.read();
            }
        };
    }
 
	@Override
	public String getHeader(String name) {
		return super.getHeader(name);
	}
 
	@Override
	public Enumeration<String> getHeaderNames() {
		return super.getHeaderNames();
	}
 
	@Override
	public Enumeration<String> getHeaders(String name) {
		return super.getHeaders(name);
	}
 
 /**
     * 获取请求Body
     *
     * @param request
     * @return
     */
    private static String getBodyString(ServletRequest request) {
        StringBuilder sb = new StringBuilder();
        InputStream inputStream = null;
        BufferedReader reader = null;
        try {
            inputStream = request.getInputStream();
            reader = new BufferedReader(new InputStreamReader(inputStream, Charset.forName("UTF-8")));
            String line = "";
            while ((line = reader.readLine()) != null) {
                sb.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return sb.toString();
    }   
}

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLDecoder;
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;
import javax.servlet.http.HttpServletResponse;
import javax.xml.crypto.URIDereferencer;
 
import com.yt.util.HttpHelper;
import com.yt.util.JsonHelper;
 
public class ContentTypeFilter implements Filter {
 
	@Override
	public void destroy() {
 
	}
 
	@Override
	public void doFilter(ServletRequest req, ServletResponse res,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest hreq = (HttpServletRequest) req;
	     //判断是否为application/json请求
	     if(application/json请求){
	        //注入我们重写的request请求
            req = new BodyReaderHttpServletRequestWrapper(hreq);
        }
       chain.doFilter(req, res);
	}
 
	@Override
	public void init(FilterConfig arg0) throws ServletException {
		
	}
}

参考文章
http://blog.csdn.net/pyxly1314/article/details/51802652