HttpClient的使用

HttpClient的Get方法

1. 首先创建一个Maven项目

2. 在pom.xml中配置Maven

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.3.1</version>
</dependency>

3. 不带参数的Get方法

CloseableHttpResponse response = null;
//打开浏览器，创建HttpClient对象
CloseableHttpClient httpClient = HttpClients.createDefault();
//输入网址，发起Get请求，创建HttpGet对象
HttpGet httpGet = new HttpGet(uriBuilder    .build());
try {
    //发起请求，返回响应
    response = httpClient.execute(httpGet);
    //解析数据，获取数据
    //判断状态码
    if (response.getStatusLine().getStatusCode()==200){
        HttpEntity entity = response.getEntity();
        String content = EntityUtils.toString(entity,"utf-8");
        System.out.println(content);
    }
} catch (IOException e) {
    e.printStackTrace();
    System.out.println("发起请求失败");
}finally {
    //释放资源
    response.close();
    httpClient.close();
}

4. 带参数的Get方法

CloseableHttpResponse response = null;
//打开浏览器，创建HttpClient对象
CloseableHttpClient httpClient = HttpClients.createDefault();
//创建URIBuilder
URIBuilder uriBuilder = new URIBuilder("http://yun.itheima.com/search");
//设置参数
uriBuilder.setParameter("keys","java");
//输入网址，发起Get请求，创建HttpGet对象
HttpGet httpGet = new HttpGet(uriBuilder    .build());

try {
    //发起请求，返回响应
    response = httpClient.execute(httpGet);
    //解析数据，获取数据
    //判断状态码
    if (response.getStatusLine().getStatusCode()==200){
        HttpEntity entity = response.getEntity();
        String content = EntityUtils.toString(entity,"utf-8");
        System.out.println(content);
    }
} catch (IOException e) {
    e.printStackTrace();
    System.out.println("发起请求失败");
}finally {
    //释放资源
    response.close();
    httpClient.close();
}

5. 不带参数的Post方法

//创建httpclient对象
CloseableHttpClient httpClient = HttpClients.createDefault();
//创建post对象
HttpPost post = new HttpPost("http://catjava.top");
//创建响应对象
//发起请求
CloseableHttpResponse response = null;
//就是把Get请求中的HttpGet换成HttpPost对象

6. 带参数的Post方法

//创建httpclient对象
CloseableHttpClient httpClient = HttpClients.createDefault();
//创建post对象
HttpPost post = new HttpPost("http://yun.itheima.com/search");
//声明List集合，封装表单中的参数
List<NameValuePair> params = new ArrayList<NameValuePair>();
//设置请求地址
params.add(new BasicNameValuePair("keys","Java"));
//创建表单中的Entity对象
UrlEncodedFormEntity encodedFormEntity = new UrlEncodedFormEntity(params,"utf-8");
//设置Enitity到post中
post.setEntity(encodedFormEntity);
//创建响应对象
//发起请求

• Post中声明一个List用来储存表单中的数据

7. 连接池

使用连接池来管理HttpClient，就不需要每次使用都创建销毁HttpClient对象。

public static void main(String[] args) throws URISyntaxException {
    //创建连接池管理器
    PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager();
    //设置最大连接数
    connectionManager.setMaxTotal(100);
    //设置每个主机的最大连接数
    connectionManager.setDefaultMaxPerRoute(10);
    //使用连接池发起请求
    doGet(connectionManager);
    doGet(connectionManager);
}

private static void doGet(PoolingHttpClientConnectionManager connectionManager) throws URISyntaxException {
    //不是创建httpclient对象，而是从连接池获取
    CloseableHttpClient httpClient = HttpClients.custom().setConnectionManager(connectionManager).build();
    //下面的就是正常的请求
     //httpclient不能直接close
            //应该由连接池管理器来管理

• 在最后释放资源的时候**不能httpclient.close()，应该由连接池来管理**

8. 请求参数

//输入网址，发起Get请求，创建HttpGet对象
HttpGet httpGet = new HttpGet(uriBuilder.build());

//配置请求信息
RequestConfig config = RequestConfig.custom().setConnectTimeout(1000)//创建连接的最长时间
        .setConnectionRequestTimeout(500)//获取连接的最长时间
        .setSocketTimeout(10*1000)//数据传输的最长时间
        .build();
//还有很多其他的设置
//给请求设置请求信息
httpGet.setConfig(config);
try {
    //发起请求，返回响应