HttpClient的GET请求（post）请求

一。不带参数的GET请求

// 创建Httpclient对象
CloseableHttpClient httpclient = HttpClients.createDefault();

// 创建http GET请求
HttpGet httpGet = new HttpGet("http://www.baidu.com/");

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) {
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println("内容长度："+content.length());
}
} finally {
if (response != null) {
response.close();
}
httpclient.close();
}

 

二。带参数的GET请求

// 创建Httpclient对象
CloseableHttpClient httpclient = HttpClients.createDefault();

// 定义请求的参数
URI uri = new URIBuilder("http://www.baidu.com/s").setParameter("wd", "java").build();

System.out.println(uri);

// 创建http GET请求
HttpGet httpGet = new HttpGet(uri);

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) {
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println(content);
}
} finally {
if (response != null) {
response.close();
}
httpclient.close();
}

 

三。不带参数的POST请求

// 创建Httpclient对象
CloseableHttpClient httpclient = HttpClients.createDefault();

// 创建http POST请求
HttpPost httpPost = new HttpPost("http://www.oschina.net/");
//设置请求头信息，可以伪装成浏览器访问
httpPost.setHeader("User-Agent","Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 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) {
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println(content);
}
} finally {
if (response != null) {
response.close();
}
httpclient.close();
}

 

四。带参数的POST请求

// 创建Httpclient对象
CloseableHttpClient httpclient = HttpClients.createDefault();

// 创建http POST请求
HttpPost httpPost = new HttpPost("http://www.oschina.net/search");

// 设置2个post参数，一个是scope、一个是q
List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
parameters.add(new BasicNameValuePair("scope", "project"));
parameters.add(new BasicNameValuePair("q", "java"));
// 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) {
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println(content);
}
} finally {
if (response != null) {
response.close();
}
httpclient.close();
}

五。如果考虑性能问题，可以跟创建数据库连接池的做法一样，这里创建一个连接池；例子如下：

PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
// 设置最大连接数
cm.setMaxTotal(200);
// 设置每个主机地址的并发数
cm.setDefaultMaxPerRoute(20);

doGet(cm);

doGet(cm);

//这里是调用

public static void doGet(HttpClientConnectionManager cm) throws Exception {
CloseableHttpClient httpClient = HttpClients.custom().setConnectionManager(cm).build();

// 创建http GET请求
HttpGet httpGet = new HttpGet("http://www.baidu.com/");

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) {
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println("内容长度：" + content.length());
}
} finally {
if (response != null) {
response.close();
}
// 此处不能关闭httpClient，如果关闭httpClient，连接池也会销毁
// httpClient.close();
}
}