使用Apache HttpClient發送和接收JSON格式的數據

JSON格式數據的優點：

　   A.數據格式比較簡單，易於讀寫，格式都是壓縮的，佔用帶寬小，是非常輕量級的數據格式；
　　B.易於解析，客戶端JavaScript可以簡單的通過eval()進行JSON數據的讀取；
　　C.支持多種語言，其中在Java端有豐富的工具操作和解析JSON；
　　D.因爲JSON格式能直接爲服務器端代碼使用，大大簡化了服務器端和客戶端的代碼開發量，且完成任務不變，並且易於維護；

由於有以上的優點，因此在項目當中，項目當中的數據通信一般都採用的是json格式的數據。在使用HttpClient調用接口的時候，就涉及如何發送和接收JSON格式的數據，操作如下：

第一步：引入maven依賴

<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.2</version>
</dependency>

第二步：寫兩個接口，第一個不接收參數直接返回json數據用來測試GET請求，第二個接收json數據返回json數據用來測試POST請求。

//直接返回json格式的字符串
@RequestMapping("/testGet")
@ResponseBody
public String testGet(){
    Map<String,String> map = Maps.newHashMap();
    map.put("paramF","第一個參數");
    map.put("paramS","第二個參數");
    return ApiResponse.buildSuccessResponse(ResultConstant.OPERATOR_SUCCESS,ResultConstant.MESSAGE_OPERATE_SUCCESS,map);
}

//接收json格式的字符串並返回json格式的字符串
@RequestMapping("/testPost")
@ResponseBody
public String testPost(@RequestBody(required = false)String requestJson){
    try{
        JSONObject jsonObject = JSON.parseObject(requestJson);
        logger.info("接收到的消息是："+jsonObject.toJSONString());
        Map<String,String> map = Maps.newHashMap();
        map.put("paramF","第一個參數");
        map.put("paramS","第二個參數");
        return ApiResponse.buildSuccessResponse(ResultConstant.OPERATOR_SUCCESS,ResultConstant.MESSAGE_OPERATE_SUCCESS,map);
    }
    catch (Exception e){
        return ApiResponse.buildFailResponse(ResultConstant.OPERATOR_FAIL,ResultConstant.MESSAGE_SYSTEM_EXCEPTION);
    }
}

public class ApiResponse implements Serializable {
    //狀態碼
    private Integer statusCode;
    //返回消息
    private String  message;
    //返回對象
    private Object data;


    public static String buildFailResponse(Integer statusCode, String message)
    {
        return JSONObject.toJSONString(new ApiResponse(statusCode,message,"NULL"));
    }


    public static String buildSuccessResponse(String message)
    {
        return JSONObject.toJSONString(new ApiResponse(ResultConstant.OPERATOR_SUCCESS,message,"NULL"));
    }


    public static String buildSuccessResponse(Integer statusCode, Object data)
    {
        return JSONObject.toJSONString(new ApiResponse(ResultConstant.OPERATOR_SUCCESS,"NULL",data));
    }


    public static String buildSuccessResponse(Integer statusCode,String message, Object data)
    {
        return JSONObject.toJSONString(new ApiResponse(ResultConstant.OPERATOR_SUCCESS,message,data));
    }


    public ApiResponse(Integer statusCode, String message, Object data) {
        this.statusCode = statusCode;
        this.message = message;
        this.data=data;
    }

    public ApiResponse(Integer statusCode, String message) {
        this.statusCode = statusCode;
        this.message = message;
    }

    public ApiResponse() {
    }

    public Integer getStatusCode() {
        return statusCode;
    }

    public void setStatusCode(Integer statusCode) {
        this.statusCode = statusCode;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public Object getData() {
        return data;
    }

    public void setData(Object data) {
        this.data = data;
    }

    @Override
    public String toString() {
        return "ApiResponse{" +
                "statusCode=" + statusCode +
                ", Message='" + message + '\'' +
                ", data=" + data +
                '}';
    }
}

第三步：使用HttpClient來發送請求獲取數據，分別測試GET和POST

     //CloseableHttpClient：建立一個可以關閉的httpClient
     //這樣使得創建出來的HTTP實體，可以被Java虛擬機回收掉，不至於出現一直佔用資源的情況。
     CloseableHttpClient closeableHttpClient = HttpClients.createDefault();

     //設置請求超時時間
     RequestConfig requestConfig = RequestConfig.custom()
             .setSocketTimeout(60000)
             .setConnectTimeout(60000)
             .setConnectionRequestTimeout(60000)
             .build();

     try {
         String url = "http://localhost:8012/testGet";//我的項目運行在8012端口
         HttpGet request = new HttpGet(url);
         //給這個請求設置請求配置
         request.setConfig(requestConfig);
         request.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64) ...");
         CloseableHttpResponse response = closeableHttpClient.execute(request);
         if(response.getStatusLine().getStatusCode()==HttpStatus.SC_OK){
             String result = EntityUtils.toString(response.getEntity());// 返回json格式：
             logger.info("GET返回過來的信息是："+result);
         }
     }
     catch (Exception e){
         logger.info("發生了異常："+e.getMessage());
     }
     finally {
         try {                //關閉流並釋放資源
             closeableHttpClient.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

得到的logger記錄如下：

GET返回過來的信息是：{"data":{"paramF":"第一個參數","paramS":"第二個參數"},"message":"操作成功","statusCode":100}

    //CloseableHttpClient：建立一個可以關閉的httpClient
    //這樣使得創建出來的HTTP實體，可以被Java虛擬機回收掉，不至於出現一直佔用資源的情況。
    CloseableHttpClient closeableHttpClient = HttpClients.createDefault();

    //設置請求超時時間
    RequestConfig requestConfig = RequestConfig.custom()
            .setSocketTimeout(60000)
            .setConnectTimeout(60000)
            .setConnectionRequestTimeout(60000)
            .build();

    try {
        HttpPost post = new HttpPost("http://localhost:8012/testPost");
        post.setConfig(requestConfig);
        //發送的參數數據
        Map<String,String> map = Maps.newHashMap();
        map.put("content","wwgfgfbb");
        map.put("value","rerrrh");
        //設置發送的數據
        StringEntity s = new StringEntity(JSON.toJSONString(map));
        s.setContentEncoding("UTF-8");
        s.setContentType("application/json");//發送json數據需要設置contentType
        post.setEntity(s);
        //獲取返回值
        CloseableHttpResponse res = closeableHttpClient.execute(post);
        if(res.getStatusLine().getStatusCode() == HttpStatus.SC_OK){
            String result = EntityUtils.toString(res.getEntity());// 返回json格式：
            logger.info("POST請求返回的數據是："+result);
        }
    }
    catch (Exception e){
        logger.info("發生了異常："+e.getMessage());
    }
    finally {
        try {                //關閉流並釋放資源
            closeableHttpClient.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

POST請求在接口端的日誌記錄：

接收到的消息是：{"value":"rerrrh","content":"wwgfgfbb"}

在請求端接收到的消息：

POST請求返回的數據是：{"data":{"paramF":"第一個參數","paramS":"第二個參數"},"message":"操作成功","statusCode":100}

通過以上的測試，都能夠正確的發送和接收JSON格式數據。

我們還可以配置CloseableHttpClient交給spring去管理，需要的時候直接給注入就行了。

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.springframework.context.annotation.Scope;

@Configuration
public class HttpClientConfig {
    @Bean
    public PoolingHttpClientConnectionManager poolingHttpClientConnectionManager() {
        PoolingHttpClientConnectionManager poolingHttpClientConnectionManager = new PoolingHttpClientConnectionManager();
        poolingHttpClientConnectionManager.setMaxTotal(10);
        poolingHttpClientConnectionManager.setDefaultMaxPerRoute(5);
        return poolingHttpClientConnectionManager;
    }
    @Bean
    public HttpClientBuilder httpClientBuilder() {
        HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
        httpClientBuilder.setConnectionManager(poolingHttpClientConnectionManager());
        return httpClientBuilder;
    }
    @Bean
    @Scope("prototype")
    public CloseableHttpClient closeableHttpClient() {
        return httpClientBuilder().build();
    }
}