如今成熟的应用必然离不开读写网络数据，而 HTTP 请求正式最普遍且常用的网络通信协议，所以掌握使用 Get 和 Post 方式进行 HTTP 通信十分必要。
核心内容：
- 使用 HTTP 的 Get 方式与 Post 方式进行网络通信。
- 使用 HttpClient 简化 HTTP 通讯操作。
一、使用 Http 的 Get 方式读取网络数据
简介：介绍使用Get方式与网络通信是最常见的 Http通信， 建立链接之后就可以通过输入流读取网络数据。
案例1: HTTP GET请求DEMO
package com.netease.hettpdemo;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
/**
* HTTP GET请求DEMO
*/
public class HTTPGetDemo {
public static void main(String[] args) {
new ReadByGet().start();
}
}
class ReadByGet extends Thread{
private static final String TEST_GET_URL="http://fanyi.youdao.com/openapi.do?wecome=";
@Override
public void run() {
try {
// 实例化URL对象
URL url=new URL(TEST_GET_URL);
// 建立并获取HTTP连接
URLConnection connection= url.openConnection();
// 获取输入流对象
InputStream is=connection.getInputStream();
// 指定解析输入流的编码格式
InputStreamReader isr=new InputStreamReader(is,"UTF-8");
// 缓存读取器
BufferedReader br=new BufferedReader(isr);
String line;
StringBuilder builder=new StringBuilder();
while ((line=br.readLine())!=null) {
builder.append(line);
}
System.out.println(builder.toString());
// 关闭各种流对象
br.close();
isr.close();
is.close();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
二、使用 Http 的 Post 方式与网络交互通信
简介：Post 方式需要向网络传输一部分数据，所以同时具有输入流和输出流。本课时讲解使用 Http 的 Post 方式与网络交互通信。
案例2：HTTP POST请求DEMO
package com.netease.hettpdemo;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class HTTPPostDemo {
public static void main(String[] args) {
ReadByPost myThread=new ReadByPost();
myThread.start();
}
}
class ReadByPost extends Thread{
@Override
public void run() {
try {
// 实例化URL对象
URL url=new URL("http://fanyi.youdao.com/openapi.do");
HttpURLConnection connection=(HttpURLConnection)url.openConnection();
connection.setRequestProperty("encoding", "UTF-8");
// 设置允许该连接从网络中获取数据
connection.setDoInput(true);
// 设置允许该连接向网络传输数据
connection.setDoOutput(true);
// 设置请求方法
connetion.setRequestMethod("POST");
// 设置请求体
OutputStream os=connection.getOutputStream();
OutputStreamWriter isw=new OutputStreamWriter(os, "UTF-8");
BufferedWriter bw=new BufferedWriter(isw);
bw.write("keyform=testHttpGet&key=850021564&type=data&doctype=xml&version=1.1&q=good");
bw.flush();
// 处理返回结果
InputStream is=connection.getInputStream();
InputStreamReader isr=new InputStreamReader(is,"UTF-8");
BufferedReader br=new BufferedReader(isr);
// 输出响应结果
String line;
while((line=br.readline())!=null){
System.out.println(line);
}
// 释放资源
is.close();
isr.close();
br.close();
os.close();
isw.close();
bw.close();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
三、使用HttpClient进行Get方式通信
maven导包：
<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.2</version>
</dependency>
案例3：HttpClient GET请求DEMO
public static final PoolingHttpClientConnectionManager CONN_MANAGER = new PoolingHttpClientConnectionManager();
public static final CloseableHttpClient HTTP_CLIENT;
public static final RequestConfig DEFAULT_REQUEST_CONFIG;
static {
CONN_MANAGER.setMaxTotal(200); // 整个连接管理器的最大连接数设
CONN_MANAGER.setDefaultMaxPerRoute(25); // 每个目标主机的最大连接数
HTTP_CLIENT = HttpClients.custom().setConnectionManager(CONN_MANAGER).build();
DEFAULT_REQUEST_CONFIG = RequestConfig.custom().setSocketTimeout(10000).setConnectTimeout(3000).build();//设置请求和传输超时时间
}
/**
* HTTP Get请求
* @param url 请求的URL地址
* @param timeout 超时时间
* @return
*/
public static String sendGet(String url, int timeout) {
HttpGet httpget = new HttpGet(url);
if (timeout > 0) {
httpget.setConfig(RequestConfig.custom().setSocketTimeout(timeout).setConnectTimeout(timeout).build());
} else {
httpget.setConfig(DEFAULT_REQUEST_CONFIG);
}
HttpEntity entity = null;
CloseableHttpResponse httpResponse=null;
try {
httpResponse = HTTP_CLIENT.execute(httpget);
entity = httpResponse.getEntity();
String content = EntityUtils.toString(entity, Charset.forName("UTF-8"));
return content;
} catch (Exception e) {
throw new RuntimeException("failed to get!", e);
} finally {
if (entity != null) {
try {
EntityUtils.consume(entity);
} catch (IOException e) {
LOG.error(e);
}
}
if(httpResponse!=null){
try {
httpResponse.close();
} catch (IOException e) {
LOG.error(e);
}
}
}
}
四、使用 HttpClient 进行 Post 方式通信
maven导包：
<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.2</version>
</dependency>
案例4：HttpClient POST请求DEMO
public static final PoolingHttpClientConnectionManager CONN_MANAGER = new PoolingHttpClientConnectionManager();
public static final CloseableHttpClient HTTP_CLIENT;
public static final RequestConfig DEFAULT_REQUEST_CONFIG;
static {
CONN_MANAGER.setMaxTotal(200); // 整个连接管理器的最大连接数设
CONN_MANAGER.setDefaultMaxPerRoute(25); // 每个目标主机的最大连接数
HTTP_CLIENT = HttpClients.custom().setConnectionManager(CONN_MANAGER).build();
DEFAULT_REQUEST_CONFIG = RequestConfig.custom().setSocketTimeout(10000).setConnectTimeout(3000).build();//设置请求和传输超时时间
}
/**
* 指定header的HTTP POST请求
* @param url 请求的URL地址
* @param params body参数
* @param headMap header参数
* @param timeout 超时时间
* @return
*/
public static String sendPost(String url, Map<String, String> params, Map<String, String> headMap, int timeout) {
HttpPost httpPost = new HttpPost(url);
httpPost.setConfig(DEFAULT_REQUEST_CONFIG);
List<NameValuePair> nvps = new ArrayList<NameValuePair>();
if (params != null) {
for (Entry<String, String> e : params.entrySet()) {
nvps.add(new BasicNameValuePair(e.getKey(), e.getValue()));
}
}
httpPost.setEntity(new UrlEncodedFormEntity(nvps, Charset.forName("UTF-8")));
if (headMap != null) {
for(Map.Entry<String, String> head : headMap.entrySet()) {
httpPost.addHeader(head.getKey(), head.getValue());
}
}
HttpEntity entity = null;
CloseableHttpResponse httpResponse = null;
try {
httpResponse = HTTP_CLIENT.execute(httpPost);
entity = httpResponse.getEntity();
String content = EntityUtils.toString(entity, Charset.forName("UTF-8"));
return content;
} catch (Exception e) {
throw new RuntimeException("failed to post!", e);
} finally {
if (entity != null) {
try {
EntityUtils.consume(entity);
} catch (IOException e) {
LOG.error(e);
}
}
if(httpResponse!=null){
try {
httpResponse.close();
} catch (IOException e) {
LOG.error(e);
}
}
}
}
