java发送http请求（提交form表单）

http://hbiao68.iteye.com/blog/1973914

写一个servlet用于测试请求

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Abc extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("doGet");
        this.doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("doPost");
        System.out.println("aaa : "+request.getParameter("aaa"));
        System.out.println("param1 : "+request.getParameter("param1"));

        System.out.println(request.getHeader("avc"));

        PrintWriter pw = response.getWriter();
        pw.write(request.getParameter("param1"));
        pw.flush();
        pw.close();
    }

}

 

web.xml配置文件

<servlet>
   <description></description>
   <display-name>Abc</display-name>
   <servlet-name>Abc</servlet-name>
   <servlet-class>com.Abc</servlet-class>
 </servlet>
 <servlet-mapping>
   <servlet-name>Abc</servlet-name>
   <url-pattern>/Abc</url-pattern>
 </servlet-mapping>

 

抽象出一个工具请求类

package http;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Map;
import java.util.Map.Entry;

public class HttpUtil {

    public static String http(String url, Map<String, String> params) {
        URL u = null;
        HttpURLConnection con = null;
        // 构建请求参数
        StringBuffer sb = new StringBuffer();
        if (params != null) {
            for (Entry<String, String> e : params.entrySet()) {
                sb.append(e.getKey());
                sb.append("=");
                sb.append(e.getValue());
                sb.append("&");
            }
            sb.substring(0, sb.length() - 1);
        }
        System.out.println("send_url:" + url);
        System.out.println("send_data:" + sb.toString());
        // 尝试发送请求
        try {
            u = new URL(url);
            con = (HttpURLConnection) u.openConnection();
            //// POST 只能为大写，严格限制，post会不识别
            con.setRequestMethod("POST");
            con.setDoOutput(true);
            con.setDoInput(true);
            con.setUseCaches(false);
            con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            OutputStreamWriter osw = new OutputStreamWriter(con.getOutputStream(), "UTF-8");
            osw.write(sb.toString());
            osw.flush();
            osw.close();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (con != null) {
                con.disconnect();
            }
        }

        // 读取返回内容
        StringBuffer buffer = new StringBuffer();
        try {
            //一定要有返回值，否则无法把请求发送给server端。
            BufferedReader br = new BufferedReader(new InputStreamReader(con.getInputStream(), "UTF-8"));
            String temp;
            while ((temp = br.readLine()) != null) {
                buffer.append(temp);
                buffer.append("\n");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        return buffer.toString();
    }

}

 备注：一定要获取返回值，否则请求无法到达。

readLine()为阻塞方法，会等待服务器的响应，否则会一直等待

con.setDoOutput(true); 这个表示是要发送请求到URL地址，没有这句话server是不会响应的。

参数的传递方式类似于在URL后面添加"?key=value&key1=value1"这种方式

 

 

测试类

@Test
    public void test3() {
        Map parames = new HashMap<String, String>();
        parames.put("param1", "param1_value");
        parames.put("param2", "param2_value");
        parames.put("param3", "param3_value");
        // 如果地址栏中有aaa这个参数，则默认选择地址栏的，如果没有则选择添加的参数
        parames.put("aaa", "aaa_value");
        HttpUtil.http("http://localhost:8080/a/Abc?aaa=dddd", parames);
    }