记录下 自己用的Java用后台发http请求并返回数据的方式

首先在pom.xml中引入

<!-- https://mvnrepository.com/artifact/com.alibaba/fastjson -->
<dependency>
　　<groupId>com.alibaba</groupId>
　　<artifactId>fastjson</artifactId>
　　<version>1.2.56</version>
</dependency>

import org.apache.http.HttpEntity;
import org.apache.http.ParseException;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;


import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONException;
import com.alibaba.fastjson.JSONObject;

/**
       * 
       * @throws Exception 
       */
      @ResponseBody
      @RequestMapping(value="getWorkFlowTempletFilter")
      public List<Map<String, Object>> getWorkFlowTempletFilter(@RequestParam("filter") String filter) throws Exception{
              String url="http://XX.XX.XX.XX:XX/workflow/getWorkFlowTempletFilter";
              if(filter !=null){
                  url +="?filter=" + filter;
              }
              System.out.println(url);
            //1.获得一个httpclient对象
            CloseableHttpClient httpclient = HttpClients.createDefault();
            //2.生成一个get请求
            HttpGet httpget = new HttpGet(url);
            CloseableHttpResponse response = null;
            try {
                //3.执行get请求并返回结果
                response = httpclient.execute(httpget);
            } catch (IOException e1) {
                e1.printStackTrace();
            }
            String result = null;
            try {
                //4.处理结果，这里将结果返回为字符串
                HttpEntity entity = response.getEntity();
                if (entity != null) {
                    result = EntityUtils.toString(entity);
                }
            } catch (ParseException | IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    response.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            List<Map<String, Object>> listMap = new ArrayList<Map<String, Object>>();
            JSONArray objectAttr = JSONArray.parseArray(result);
            Map<String, Object> retMap = new HashMap<String, Object>();
            if(objectAttr.size()>0){
                for(int i=0;i<objectAttr.size();i++){
                    JSONObject jsonObject = objectAttr.getJSONObject(i);
                    retMap = toMap(jsonObject);
                    listMap.add(retMap);
                    
                }
            }
           
            return listMap;
         
      }
      
      public static Map<String, Object> toMap(JSONObject object) throws JSONException {
            Map<String, Object> map = new HashMap<String, Object>();

            Set<String> keysItr =  object.keySet();
            Iterator<String> it = keysItr.iterator(); 
            while(it.hasNext()) {
                String key = it.next();
                Object value = object.get(key);
                map.put(key, value);
            }
            return map;
        }
      /*
      public static Map<String, Object> toMap(JSONObject object) throws JSONException {
            Map<String, Object> map = new HashMap<String, Object>();

            Iterator<String> keysItr =  (Iterator<String>) object.keySet();
            while(keysItr.hasNext()) {
                String key = keysItr.next();
                Object value = object.get(key);

                if(value instanceof JSONArray) {
                    value = toList((JSONArray) value);
                }

                else if(value instanceof JSONObject) {
                    value = toMap((JSONObject) value);
                }
                map.put(key, value);
            }
            return map;
        }

        public static List<Object> toList(JSONArray array) throws JSONException {
            List<Object> list = new ArrayList<Object>();
            for(int i = 0; i < array.size(); i++) {
                Object value = array.get(i);
                if(value instanceof JSONArray) {
                    value = toList((JSONArray) value);
                }

                else if(value instanceof JSONObject) {
                    value = toMap((JSONObject) value);
                }
                list.add(value);
            }
            return list;
        }  */