HttpClient
什么是HttpClient
HttpClient 是Apache Jakarta Common 下的子项目，可以用来提供高效的、最新的、功能丰富的支持 HTTP 协议的客户端编程工具包，并且它支持 HTTP 协议最新的版本和建议。
特点：
HttpClient别名：HttpComponents
HttpClient可以发送get、post、put、delete、...等请求
入门案例
导入maven坐标
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.4</version>
</dependency>
发起Get请求
1创建一个客户端 CloseableHttpClient
2创建一个get方法请求实例 HttpGet
3发送请求 execute
4获取响应的头信息
5获取响应的主题内容
6关闭响应对象
使用HttpClient发起Get请求的案例代码：
public class DoGET {
public static void main(String[] args) throws Exception {
// 创建Httpclient对象,相当于打开了浏览器
CloseableHttpClient httpclient = HttpClients.createDefault();
// 创建HttpGet请求，相当于在浏览器输入地址
HttpGet httpGet = new HttpGet("http://www.baidu.com/");
CloseableHttpResponse response = null;
try {
// 执行请求，相当于敲完地址后按下回车。获取响应
response = httpclient.execute(httpGet);
// 判断返回状态是否为200
if (response.getStatusLine().getStatusCode() == 200) {
// 解析响应，获取数据
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println(content);
}
} finally {
if (response != null) {
// 关闭资源
response.close();
}
// 关闭浏览器
httpclient.close();
}
}
}
带参数的Get请求
1创建一个客户端 CloseableHttpClient
2 通过URIBuilder传递参数
3创建一个get方法请求实例 HttpGet
4发送请求 execute
5获取响应的头信息
6获取响应的主题内容
7关闭响应对象
访问网站的爬虫协议：
public class DoGETParam {
public static void main(String[] args) throws Exception {
// 创建Httpclient对象
CloseableHttpClient httpclient = HttpClients.createDefault();
// 创建URI对象，并且设置请求参数
URI uri = new URIBuilder("http://www.baidu.com/s").setParameter("wd", "java").build();
// 创建http GET请求
HttpGet httpGet = new HttpGet(uri);
// HttpGet get = new HttpGet("http://www.baidu.com/s?wd=java");
CloseableHttpResponse response = null;
try {
// 执行请求
response = httpclient.execute(httpGet);
// 判断返回状态是否为200
if (response.getStatusLine().getStatusCode() == 200) {
// 解析响应数据
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println(content);
}
} finally {
if (response != null) {
response.close();
}
httpclient.close();
}
}
}
发起POST请求
/*
* 演示：使用HttpClient发起POST请求
*/
public class DoPOST {
public static void main(String[] args) throws Exception {
// 创建Httpclient对象
CloseableHttpClient httpclient = HttpClients.createDefault();
// 创建http POST请求
HttpPost httpPost = new HttpPost("http://www.oschina.net/");
// 把自己伪装成浏览器。否则开源中国会拦截访问
httpPost.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36");
CloseableHttpResponse response = null;
try {
// 执行请求
response = httpclient.execute(httpPost);
// 判断返回状态是否为200
if (response.getStatusLine().getStatusCode() == 200) {
// 解析响应数据
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println(content);
}
} finally {
if (response != null) {
response.close();
}
// 关闭浏览器
httpclient.close();
}
}
}
带参数POST请求
/*
* 演示：使用HttpClient发起带有参数的POST请求
*/
public class DoPOSTParam {
public static void main(String[] args) throws Exception {
// 创建Httpclient对象
CloseableHttpClient httpclient = HttpClients.createDefault();
// 创建http POST请求，访问开源中国
HttpPost httpPost = new HttpPost("http://www.oschina.net/search");
// 根据开源中国的请求需要，设置post请求参数
List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
parameters.add(new BasicNameValuePair("scope", "project"));
parameters.add(new BasicNameValuePair("q", "java"));
parameters.add(new BasicNameValuePair("fromerr", "8bDnUWwC"));
// 构造一个form表单式的实体
UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters);
// 将请求实体设置到httpPost对象中
httpPost.setEntity(formEntity);
CloseableHttpResponse response = null;
try {
// 执行请求
response = httpclient.execute(httpPost);
// 判断返回状态是否为200
if (response.getStatusLine().getStatusCode() == 200) {
// 解析响应体
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println(content);
}
} finally {
if (response != null) {
response.close();
}
// 关闭浏览器
httpclient.close();
}
}
}
SpringBoot整合HttpClient
SpringBoot官方并没有对HttpClient的启动器。所以我们需要自己完成配置，还好，我们刚才在测试案例中已经写过了。
不过，SpringBoot虽然没有提供启动器，但是却提供了一个统一的对Restful服务进行调用的模板类：RestTemplate，底层可以使用HttpClient来实现。有了这个我们就无需自己定义APIService了。
1、导入maven坐标
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>
2、在application.properties添加如下配置:
#The config for HttpClient
http.maxTotal=300
http.defaultMaxPerRoute=50
http.connectTimeout=1000
http.connectionRequestTimeout=500
http.socketTimeout=5000
http.staleConnectionCheckEnabled=true
3、 创建HttpClientConfig类--类似util
在类中编写代码
/**
* HttpClient的配置类
*
*/
@Configuration
@ConfigurationProperties(prefix = "http", ignoreUnknownFields = true)
public class HttpClientConfig {
private Integer maxTotal;// 最大连接
private Integer defaultMaxPerRoute;// 每个host的最大连接
private Integer connectTimeout;// 连接超时时间
private Integer connectionRequestTimeout;// 请求超时时间
private Integer socketTimeout;// 响应超时时间
/**
* HttpClient连接池
* @return
*/
@Bean
public HttpClientConnectionManager httpClientConnectionManager() {
PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager();
connectionManager.setMaxTotal(maxTotal);
connectionManager.setDefaultMaxPerRoute(defaultMaxPerRoute);
return connectionManager;
}
/**
* 注册RequestConfig
* @return
*/
@Bean
public RequestConfig requestConfig() {
return RequestConfig.custom().setConnectTimeout(connectTimeout)
.setConnectionRequestTimeout(connectionRequestTimeout).setSocketTimeout(socketTimeout)
.build();
}
/**
* 注册HttpClient
* @param manager
* @param config
* @return
*/
@Bean
public HttpClient httpClient(HttpClientConnectionManager manager, RequestConfig config) {
return HttpClientBuilder.create().setConnectionManager(manager).setDefaultRequestConfig(config)
.build();
}
/**
* 使用连接池管理连接
* @param httpClient
* @return
*/
@Bean
public ClientHttpRequestFactory requestFactory(HttpClient httpClient) {
return new HttpComponentsClientHttpRequestFactory(httpClient);
}
/**
* 使用HttpClient来初始化一个RestTemplate
* @param requestFactory
* @return
*/
@Bean
public RestTemplate restTemplate(ClientHttpRequestFactory requestFactory) {
RestTemplate template = new RestTemplate(requestFactory);
List<HttpMessageConverter<?>> list = template.getMessageConverters();
for (HttpMessageConverter<?> mc : list) {
if (mc instanceof StringHttpMessageConverter) {
((StringHttpMessageConverter) mc).setDefaultCharset(Charset.forName("UTF-8"));
}
}
return template;
}
public Integer getMaxTotal() {
return maxTotal;
}
public void setMaxTotal(Integer maxTotal) {
this.maxTotal = maxTotal;
}
public Integer getDefaultMaxPerRoute() {
return defaultMaxPerRoute;
}
public void setDefaultMaxPerRoute(Integer defaultMaxPerRoute) {
this.defaultMaxPerRoute = defaultMaxPerRoute;
}
public Integer getConnectTimeout() {
return connectTimeout;
}
public void setConnectTimeout(Integer connectTimeout) {
this.connectTimeout = connectTimeout;
}
public Integer getConnectionRequestTimeout() {
return connectionRequestTimeout;
}
public void setConnectionRequestTimeout(Integer connectionRequestTimeout) {
this.connectionRequestTimeout = connectionRequestTimeout;
}
public Integer getSocketTimeout() {
return socketTimeout;
}
public void setSocketTimeout(Integer socketTimeout) {
this.socketTimeout = socketTimeout;
}
}