第一步：编写Controller，让后台去请求接口

package controller;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

import service.BillsService;
import util.Page;
import annotation.ControllerPointcut;

import com.alibaba.fastjson.JSON;

import entity.Bills;

@Controller
@RequestMapping("/bills")
public class BillsController {

@RequestMapping(value="/getTest",produces={"application/json;charset=UTF-8"})
@ResponseBody
public String getTest(@RequestParam(value="num1",required=false) String num1,@RequestParam(value="num2",required=false) String num2){
Integer sum=Integer.parseInt(num1)+Integer.parseInt(num2);
return JSON.toJSONString(sum);
}

}

第二步：启动web项目，这里项目名tally，项目请求地址是：http://localhost:8080/tally

第三步：也是最重要的一步，编写方法，后台get请求目标

package com.bingo.qing;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.Map;

public class HttpRequest {

/**
* 向指定URL发送GET方法的请求
*
* @param url
* 发送请求的URL
* @param param
* 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
* @return URL 所代表远程资源的响应结果
*/
public static String sendGet(String url, String param) {
String result = "";
BufferedReader in = null;
try {
String urlNameString = url + "?" + param;
URL realUrl = new URL(urlNameString);
// 打开和URL之间的连接
URLConnection connection = realUrl.openConnection();
// 设置通用的请求属性
connection.setRequestProperty("accept", "*/*");
connection.setRequestProperty("connection", "Keep-Alive");
connection.setRequestProperty("user-agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
// 建立实际的连接
connection.connect();
// 获取所有响应头字段
Map<String, List<String>> map = connection.getHeaderFields();
// 遍历所有的响应头字段
for (String key : map.keySet()) {
System.out.println(key + "--->" + map.get(key));
}
// 定义 BufferedReader输入流来读取URL的响应
in = new BufferedReader(new InputStreamReader(
connection.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
} catch (Exception e) {
System.out.println("发送GET请求出现异常！" + e);
e.printStackTrace();
}
// 使用finally块来关闭输入流
finally {
try {
if (in != null) {
in.close();
}
} catch (Exception e2) {
e2.printStackTrace();
}
}
return result;
}

public static void main(String[] args) {

//发送 POST 请求
String sr=HttpRequest.sendPost("http://localhost:8080/tally/bills/PostTest", "num1=456&num2=123");
System.out.println(sr);
}

}

第四步：启动main方法，返回结果如下