HttpClient 使用详解

小咪咪 2021-12-04 07:41 479阅读 0赞

## HttpClient 介绍 ##

HTTP协议是Hyper Text Transfer Protocol（超文本传输协议）的缩写,是用于从万维网（WWW:World Wide Web ）服务器传输超文本到本地浏览器的传送协议。。

HTTP是一个基于TCP/IP通信协议来传递数据（HTML 文件, 图片文件, 查询结果等）。

HttpClient 就是帮我们实现了所有的Http的方法，比如Get，Post，Put，Delete 等，同时支持Https协议等。

--------------------

## HttpClient 使用前的准备工作 ##

添加pom依赖

<dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <version>4.5.3</version>
    </dependency>
    
    
    <dependency>
    	<groupId>com.google.code.gson</groupId>
    	<artifactId>gson</artifactId>
    	<version>2.8.5</version>
    </dependency>

--------------------

##  基本使用方法  ##

无论多复杂的请求，都可以分为以下几步

1、创建 HttpClient

2、创建请求

3、执行请求并获取参数

简单理解可以为：1、打开浏览器；2、输入网址；3、回车并查看页面返回的内容；

下面具体介绍用法

--------------------

> ## Get（无入参，返回一个实体） ##

postman：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5oYW9fY19o_size_16_color_FFFFFF_t_70][]

java代码实现：

@Test
      public void getNoPara() {
        // 0.请求的 uri
        String uri = "http://localhost:8080/sell/buyer/product/one";
        // 1.创建 HttpClient
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
        // 2.创建 Get 请求
        HttpGet httpGet = new HttpGet(uri);
    
        // 3.初始化响应
        CloseableHttpResponse response = null;
    
        // 4.执行请求 Get 请求
        try {
          response = httpClient.execute(httpGet);
    
          // 从响应中获取实体
          HttpEntity responseEntity = response.getEntity();
    
          // 响应码
          System.out.println("响应状态码" + response.getStatusLine());
    
          // 响应内容转为string
          String entityString = EntityUtils.toString(responseEntity);
          // json转为对象
          ObjectMapper mapper = new ObjectMapper();
          ProductInfo productInfo = mapper.readValue(entityString, ProductInfo.class);
          System.out.println(productInfo);
        } catch (IOException e) {
          e.printStackTrace();
        }finally {
    
          // 释放连接
          try {
            if(httpClient!=null){
              httpClient.close();
            }
            if(response!=null){
              response.close();
            }
          } catch (IOException e) {
            e.printStackTrace();
          }
    
        }
    
      }

--------------------

> ## Get（无入参，返回一个封装VO） ##

postman：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5oYW9fY19o_size_16_color_FFFFFF_t_70 1][]

java代码实现：

package com.xmlParsing.entity;
    
    public class ResultVO<T> {
    
      private Integer code;
      private String msg;
      private T data;
    
    
      @Override
      public String toString() {
        return "ResultVO{" +
            "code=" + code +
            ", msg='" + msg + '\'' +
            ", data=" + data +
            '}';
      }
    
      public Integer getCode() {
    
        return code;
      }
    
      public void setCode(Integer code) {
        this.code = code;
      }
    
      public String getMsg() {
        return msg;
      }
    
      public void setMsg(String msg) {
        this.msg = msg;
      }
    
      public T getData() {
        return data;
      }
    
      public void setData(T data) {
        this.data = data;
      }
    }

@Test
      public void getNoPara() {
        // 0.请求的 uri
        String uri = "http://localhost:8080/sell/buyer/product/formatOne";
        // 1.创建 HttpClient
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
        // 2.创建 Get 请求
        HttpGet httpGet = new HttpGet(uri);
    
        // 3.初始化响应
        CloseableHttpResponse response = null;
    
        // 4.执行请求 Get 请求
        try {
          response = httpClient.execute(httpGet);
    
          // 从响应中获取实体
          HttpEntity responseEntity = response.getEntity();
    
          // 响应码
          System.out.println("响应状态码" + response.getStatusLine());
    
          // 响应内容转为string
          String entityString = EntityUtils.toString(responseEntity);
          // json转为对象
          ObjectMapper mapper = new ObjectMapper();
          ResultVO resultVO = mapper.readValue(entityString, ResultVO.class);
          System.out.println(resultVO.getData());
        } catch (IOException e) {
          e.printStackTrace();
        }finally {
    
          // 释放连接
          try {
            if(httpClient!=null){
              httpClient.close();
            }
            if(response!=null){
              response.close();
            }
          } catch (IOException e) {
            e.printStackTrace();
          }
    
        }
    
      }

--------------------

> ## Get（无入参，返回一个List） ##

postman:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5oYW9fY19o_size_16_color_FFFFFF_t_70 2][]

java代码实现:

@Test
      public void getNoPara() {
        // 0.请求的 uri
        String uri = "http://localhost:8080/sell/buyer/product/all";
        // 1.创建 HttpClient
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
        // 2.创建 Get 请求
        HttpGet httpGet = new HttpGet(uri);
    
        // 3.初始化响应
        CloseableHttpResponse response = null;
    
        // 4.执行请求 Get 请求
        try {
          response = httpClient.execute(httpGet);
    
          // 从响应中获取实体
          HttpEntity responseEntity = response.getEntity();
    
          // 响应码
          System.out.println("响应状态码" + response.getStatusLine());
    
          // 响应内容转为string
          String entityString = EntityUtils.toString(responseEntity);
          // json转为对象
          ObjectMapper mapper = new ObjectMapper();
          List<ProductInfo> list = mapper
              .readValue(entityString, new TypeReference<List<ProductInfo>>() {});
    
          list.stream().forEach(p -> System.out.println(p));
    
    
        } catch (IOException e) {
          e.printStackTrace();
        }finally {
    
          // 释放连接
          try {
            if(httpClient!=null){
              httpClient.close();
            }
            if(response!=null){
              response.close();
            }
          } catch (IOException e) {
            e.printStackTrace();
          }
    
        }
    
      }

--------------------

> ## Get（有入参） ##

postman:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5oYW9fY19o_size_16_color_FFFFFF_t_70 3][]

java代码实现:

@Test
      public void getResult() {
    
        // 1、 创建 httpClient
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
    
        // 2、定义uri 并创建 Get 请求
        URI uri = null;
        try {
          uri = new URIBuilder().setScheme("http").setHost("localhost").setPort(8080)
              .setPath("/sell/buyer/product/getResult").setParameter("value", "假装我是入参").build();
        } catch (URISyntaxException e) {
          e.printStackTrace();
        }
    
        HttpGet get = new HttpGet(uri);
    
        // 3、 初始化响应
        CloseableHttpResponse response = null;
    
    
        // 4、 执行 Get 请求
        try {
          response = httpClient.execute(get);
    
          HttpEntity responseEntity = response.getEntity();
          
          // 响应码
          System.out.println("响应状态码" + response.getStatusLine());
    
          // 响应内容转为string
          String entityString = EntityUtils.toString(responseEntity);
          System.out.println(entityString);
        } catch (IOException e) {
          e.printStackTrace();
        }finally {
    
          // 释放连接
          try {
            if(httpClient!=null){
              httpClient.close();
            }
            if(response!=null){
              response.close();
            }
          } catch (IOException e) {
            e.printStackTrace();
          }
    
        }
      }

--------------------

> ## Post（无入参） ##

postman:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5oYW9fY19o_size_16_color_FFFFFF_t_70 4][]

java代码实现：

public void postSimple() {
        // 1、创建 HttpClient
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
    
        // 2、创建 post 请求
        URI uri = null;
        try {
          uri = new URIBuilder().setScheme("http").setHost("localhost").setPort(8080)
              .setPath("/sell/buyer/product/product").build();
        } catch (URISyntaxException e) {
          e.printStackTrace();
        }
        HttpPost post = new HttpPost(uri);
    
        // 3、初始化 response
        CloseableHttpResponse response = null;
    
        // 4、执行请求
        try {
          response = httpClient.execute(post);
          HttpEntity entity = response.getEntity();
    
          // 响应内容转为string
          String entityString = EntityUtils.toString(entity);
          // json转为对象
          Gson gson = new Gson().newBuilder().serializeNulls().create();
          ResultVO resultVO = gson.fromJson(entityString, ResultVO.class);
          List<ProductInfo> list = (List<ProductInfo>) resultVO.getData();
          System.out.println(list);
    
    //      list.stream().forEach(productInfo -> System.out.println(productInfo.toString()));
        } catch (IOException e) {
          e.printStackTrace();
        } finally {
          try {
            // 释放资源
            if (httpClient != null) {
              httpClient.close();
            }
            if (response != null) {
              response.close();
            }
          } catch (IOException e) {
            e.printStackTrace();
          }
        }
      }

--------------------

> ## Post有参 ##

postman：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5oYW9fY19o_size_16_color_FFFFFF_t_70 5][]

java代码实现:

public void saveProduct() {
        // 1、构建入参对象
        ProductInfo productInfo = new ProductInfo();
        productInfo.setProductId("99999");
        productInfo.setProductName("大白菜");
        productInfo.setProductPrice(new BigDecimal("12.34"));
        productInfo.setProductStock(999);
        productInfo.setProductDescription("假装很有范的大白菜~~~~");
        productInfo.setProductIcon("noIcon");
        productInfo.setProductStatus(1);
        productInfo.setCategoryType(1);
        productInfo.setCreateTime(null);
        productInfo.setUpdateTime(null);
    
        // 2、构建 stringEntity
        Gson gson = new Gson().newBuilder().serializeNulls().create();
        String s = gson.toJson(productInfo);
        StringEntity entity = new StringEntity(s, "UTF-8");
    
        // 3、创建httpClient
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
    
        // 4、创建 post 请求
        HttpPost post = new HttpPost("http://localhost:8080/sell/buyer/product/saveProduct");
        post.setEntity(entity);
        post.setHeader("Content-Type", "application/json;charset=utf8");
    
        // 5、创建相应
        CloseableHttpResponse response = null;
        try {
          response = httpClient.execute(post);
          HttpEntity responseEntity = response.getEntity();
          // 响应内容转为string
          String entityString = EntityUtils.toString(responseEntity);
          System.out.println(entityString);
    
        } catch (IOException e) {
          e.printStackTrace();
        }finally {
          try {
            // 释放资源
            if (httpClient != null) {
              httpClient.close();
            }
            if (response != null) {
              response.close();
            }
          } catch (IOException e) {
            e.printStackTrace();
          }
        }
    
    
      }

--------------------

> ## Post(复杂入参) ##

postman :

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5oYW9fY19o_size_16_color_FFFFFF_t_70 6][]

java代码实现:

public void saveProduct() {
        // 1、构建入参对象
        ProductInfo productInfo = new ProductInfo();
        productInfo.setProductId("123999");
        productInfo.setProductName("大白菜");
        productInfo.setProductPrice(new BigDecimal("12.34"));
        productInfo.setProductStock(999);
        productInfo.setProductDescription("假装很有范的大白菜~~~~");
        productInfo.setProductIcon("noIcon");
        productInfo.setProductStatus(1);
        productInfo.setCategoryType(1);
        productInfo.setCreateTime(null);
        productInfo.setUpdateTime(null);
    
        // 2、构建 stringEntity
        Gson gson = new Gson().newBuilder().serializeNulls().create();
        String s = gson.toJson(productInfo);
        StringEntity entity = new StringEntity(s, "UTF-8");
    
        // 3、创建httpClient
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
    
        // 4、创建 复杂 带参 uri
        List<NameValuePair> parameters = new ArrayList<>();
        parameters.add(new BasicNameValuePair("date",LocalDate.now().toString()));
        parameters.add(new BasicNameValuePair("time", LocalTime.now().toString()));
        URI uri = null;
        try {
          uri = new URIBuilder().setScheme("http").setHost("localhost").setPort(8080)
              .setPath("/sell/buyer/product/saveProduct").setParameters(parameters).build();
        } catch (URISyntaxException e) {
          e.printStackTrace();
        }
    
        // 5、创建 复杂 post 请求
        HttpPost post = new HttpPost(uri);
        post.setEntity(entity);
        post.setHeader("Content-Type", "application/json;charset=utf8");
    
        // 6、创建 响应
        CloseableHttpResponse response = null;
        try {
    
          response = httpClient.execute(post);
          HttpEntity responseEntity = response.getEntity();
          String entityStr = EntityUtils.toString(responseEntity);
          System.out.println(entityStr);
    
        } catch (IOException e) {
          e.printStackTrace();
        }finally {
          try {
            // 释放资源
            if (httpClient != null) {
              httpClient.close();
            }
            if (response != null) {
              response.close();
            }
          } catch (IOException e) {
            e.printStackTrace();
          }
        }
    
      }

参考文献：[https://blog.csdn.net/justry\_deng/article/details/81042379][https_blog.csdn.net_justry_deng_article_details_81042379]

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[https_blog.csdn.net_justry_deng_article_details_81042379]: https://blog.csdn.net/justry_deng/article/details/81042379