1.使用jdk提供的URLConnection
2.使用apache提供的HttpClient（封装了jdk）
一、使用URLConnect进行http请求
public static void main(String[] args) {
//发送 GET 请求
String s=HttpRequest.sendGet("http://baidu.com", "key=123&v=456");
System.out.println(s);
//发送 POST 请求
String sr=HttpRequest.sendPost("http://baidu.com", "key=123&v=456");
System.out.println(sr);
}
/**
* 向指定URL发送GET方法的请求
*
* @param url 发送请求的URL
* @param param 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
* @return URL 所代表远程资源的响应结果
*/
public static String sendGet(String url, String param) {
String result = "";
BufferedReader in = null;
try {
String urlNameString = url + "?" + param;
URL realUrl = new URL(urlNameString);
// 打开和URL之间的连接
URLConnection connection = realUrl.openConnection();
// 设置通用的请求属性
connection.setRequestProperty("accept", "*/*");
connection.setRequestProperty("connection", "Keep-Alive");
connection.setRequestProperty("user-agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
// 建立实际的连接
connection.connect();
// 获取所有响应头字段
Map<String, List<String>> map = connection.getHeaderFields();
// 遍历所有的响应头字段
for (String key : map.keySet()) {
System.out.println(key + "--->" + map.get(key));
}
// 定义 BufferedReader输入流来读取URL的响应
in = new BufferedReader(new InputStreamReader(
connection.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
} catch (Exception e) {
System.out.println("发送GET请求出现异常！" + e);
e.printStackTrace();
}
// 使用finally块来关闭输入流
finally {
try {
if (in != null) {
in.close();
}
} catch (Exception e2) {
e2.printStackTrace();
}
}
return result;
}
/**
* 向指定 URL 发送POST方法的请求
*
* @param url 发送请求的 URL
* @param param 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
* @return 所代表远程资源的响应结果
*/
public static String sendPost(String url, String param) {
PrintWriter out = null;
BufferedReader in = null;
String result = "";
try {
URL realUrl = new URL(url);
// 打开和URL之间的连接
URLConnection conn = realUrl.openConnection();
// 设置通用的请求属性
conn.setRequestProperty("accept", "*/*");
conn.setRequestProperty("connection", "Keep-Alive");
conn.setRequestProperty("user-agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
// 发送POST请求必须设置如下两行
conn.setDoOutput(true);
conn.setDoInput(true);
// 获取URLConnection对象对应的输出流
out = new PrintWriter(conn.getOutputStream());
// 发送请求参数
out.print(param);
// flush输出流的缓冲
out.flush();
// 定义BufferedReader输入流来读取URL的响应
in = new BufferedReader(
new InputStreamReader(conn.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
} catch (Exception e) {
System.out.println("发送 POST 请求出现异常！" + e);
e.printStackTrace();
}
//使用finally块来关闭输出流、输入流
finally {
try {
if (out != null) {
out.close();
}
if (in != null) {
in.close();
}
} catch (IOException ex) {
ex.printStackTrace();
}
}
return result;
}二、使用HttpClient进行http请求
maven依赖：
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.3</version>
</dependency>public static void main(String[] args) {
get();
post();
}
public static void get(){
/**
* client和response需要关闭资源
*/
//创建client,放入try()中自动释放,不需要finally
try (CloseableHttpClient client = HttpClientBuilder.create().build()){
//执行得到response
try (CloseableHttpResponse response = client.execute(new HttpGet("http://www.baidu.com"))){
//获取statusCode
Integer statusCode = response.getStatusLine().getStatusCode();
HttpEntity entity = response.getEntity();
if (entity != null) {
//body
String bodyAsString = EntityUtils.toString(entity);
//Media Type
String contentMimeType = ContentType.getOrDefault(entity).getMimeType();
//head
Header[] headers = response.getHeaders(HttpHeaders.CONTENT_TYPE);
//输出
System.out.println("statusCode:"+statusCode);
System.out.println("contentMinmeType:"+contentMimeType);
System.out.println("body:"+bodyAsString);
System.out.println("head"+headers);
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
public static void post(){
//创建client
try (CloseableHttpClient client = HttpClientBuilder.create().build()){
HttpPost postRequest = new HttpPost("http://www.baidu.com");
//添加请求参数
List<NameValuePair> params = new ArrayList<>();
params.add(new BasicNameValuePair("key1", "value1"));
params.add(new BasicNameValuePair("key2", "value2"));
postRequest.setEntity(new UrlEncodedFormEntity(params, Consts.UTF_8));
//执行并获取返回结果到response
try (CloseableHttpResponse response = client.execute(postRequest)) {
//获取statusCode
Integer statusCode = response.getStatusLine().getStatusCode();
//Media Type
String contentMimeType = ContentType.getOrDefault(response.getEntity()).getMimeType();
//body
String bodyAsString = EntityUtils.toString(response.getEntity());
//head
Header[] headers = response.getHeaders(HttpHeaders.CONTENT_TYPE);
System.out.println("statusCode:"+statusCode);
System.out.println("contentMinmeType:"+contentMimeType);
System.out.println("body:"+bodyAsString);
System.out.println("head"+headers);
}
} catch (IOException e) {
e.printStackTrace();
}
}代码：https://github.com/ludonglue/httpRequest
参考内容：
URLConnection：http://blog.csdn.net/iijse/article/details/6201101
HttpClient：http://www.baeldung.com/httpclient-guide