本文将从代码的角度去引导如何使用httpclient的各个功能和特性。
第一个程序
import org.apache.commons.httpclient.*;
import org.apache.commons.httpclient.methods.*;
import org.apache.commons.httpclient.params.HttpMethodParams;
import java.io.*;
public class HttpClientTutorial {
private static String url = "http://www.apache.org/";
public static void main(String[] args) {
// Create an instance of HttpClient.
HttpClient client = new HttpClient();
// Create a method instance.
GetMethod method = new GetMethod(url);
// Provide custom retry handler is necessary
method.getParams().setParameter(HttpMethodParams.RETRY_HANDLER,
new DefaultHttpMethodRetryHandler(3, false));
try {
// Execute the method.
int statusCode = client.executeMethod(method);
if (statusCode != HttpStatus.SC_OK) {
System.err.println("Method failed: " + method.getStatusLine());
}
// Read the response body.
byte[] responseBody = method.getResponseBody();
// Deal with the response.
// Use caution: ensure correct character encoding and is not binary data
System.out.println(new String(responseBody));
} catch (HttpException e) {
System.err.println("Fatal protocol violation: " + e.getMessage());
e.printStackTrace();
} catch (IOException e) {
System.err.println("Fatal transport error: " + e.getMessage());
e.printStackTrace();
} finally {
// Release the connection.
method.releaseConnection();
}
}
}
模拟http网页登入
package org.apache.http.examples.client;
import java.net.URI;
import java.util.List;
import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.client.methods.RequestBuilder;
import org.apache.http.cookie.Cookie;
import org.apache.http.impl.client.BasicCookieStore;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
/**
* A example that demonstrates how HttpClient APIs can be used to perform
* form-based logon.
*/
public class ClientFormLogin {
public static void main(String[] args) throws Exception {
BasicCookieStore cookieStore = new BasicCookieStore();
CloseableHttpClient httpclient = HttpClients.custom()
.setDefaultCookieStore(cookieStore)
.build();
try {
HttpGet httpget = new HttpGet("https://someportal/");
CloseableHttpResponse response1 = httpclient.execute(httpget);
try {
HttpEntity entity = response1.getEntity();
System.out.println("Login form get: " + response1.getStatusLine());
EntityUtils.consume(entity);
System.out.println("Initial set of cookies:");
List<Cookie> cookies = cookieStore.getCookies();
if (cookies.isEmpty()) {
System.out.println("None");
} else {
for (int i = 0; i < cookies.size(); i++) {
System.out.println("- " + cookies.get(i).toString());
}
}
} finally {
response1.close();
}
HttpUriRequest login = RequestBuilder.post()
.setUri(new URI("https://someportal/"))
.addParameter("IDToken1", "username")
.addParameter("IDToken2", "password")
.build();
CloseableHttpResponse response2 = httpclient.execute(login);
try {
HttpEntity entity = response2.getEntity();
System.out.println("Login form get: " + response2.getStatusLine());
EntityUtils.consume(entity);
System.out.println("Post logon cookies:");
List<Cookie> cookies = cookieStore.getCookies();
if (cookies.isEmpty()) {
System.out.println("None");
} else {
for (int i = 0; i < cookies.size(); i++) {
System.out.println("- " + cookies.get(i).toString());
}
}
} finally {
response2.close();
}
} finally {
httpclient.close();
}
}
}
多表单Post示例
/**
* Example how to use multipart/form encoded POST request.
*/
public class ClientMultipartFormPost {
public static void main(String[] args) throws Exception {
if (args.length != 1) {
System.out.println("File path not given");
System.exit(1);
}
CloseableHttpClient httpclient = HttpClients.createDefault();
try {
HttpPost httppost = new HttpPost("http://localhost:8080" +
"/servlets-examples/servlet/RequestInfoExample");
FileBody bin = new FileBody(new File(args[0]));
StringBody comment = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN);
HttpEntity reqEntity = MultipartEntityBuilder.create()
.addPart("bin", bin)
.addPart("comment", comment)
.build();
httppost.setEntity(reqEntity);
System.out.println("executing request " + httppost.getRequestLine());
CloseableHttpResponse response = httpclient.execute(httppost);
try {
System.out.println("----------------------------------------");
System.out.println(response.getStatusLine());
HttpEntity resEntity = response.getEntity();
if (resEntity != null) {
System.out.println("Response content length: " + resEntity.getContentLength());
}
EntityUtils.consume(resEntity);
} finally {
response.close();
}
} finally {
httpclient.close();
}
}
}
用ResponseHandler来简化对http response的处理和资源释放
/**
* This example demonstrates the use of the {@link ResponseHandler} to simplify
* the process of processing the HTTP response and releasing associated resources.
*/
public class ClientWithResponseHandler {
public final static void main(String[] args) throws Exception {
CloseableHttpClient httpclient = HttpClients.createDefault();
try {
HttpGet httpget = new HttpGet("http://localhost/");
System.out.println("Executing request " + httpget.getRequestLine());
// Create a custom response handler
ResponseHandler<String> responseHandler = new ResponseHandler<String>() {
public String handleResponse(
final HttpResponse response) throws ClientProtocolException, IOException {
int status = response.getStatusLine().getStatusCode();
if (status >= 200 && status < 300) {
HttpEntity entity = response.getEntity();
return entity != null ? EntityUtils.toString(entity) : null;
} else {
throw new ClientProtocolException("Unexpected response status: " + status);
}
}
};
String responseBody = httpclient.execute(httpget, responseHandler);
System.out.println("----------------------------------------");
System.out.println(responseBody);
} finally {
httpclient.close();
}
}
}
多线程环境下GET方法的使用示例
/**
* An example that performs GETs from multiple threads.
*
*/
public class ClientMultiThreadedExecution {
public static void main(String[] args) throws Exception {
// Create an HttpClient with the ThreadSafeClientConnManager.
// This connection manager must be used if more than one thread will
// be using the HttpClient.
PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
cm.setMaxTotal(100);
CloseableHttpClient httpclient = HttpClients.custom()
.setConnectionManager(cm)
.build();
try {
// create an array of URIs to perform GETs on
String[] urisToGet = {
"http://hc.apache.org/",
"http://hc.apache.org/httpcomponents-core-ga/",
"http://hc.apache.org/httpcomponents-client-ga/",
};
// create a thread for each URI
GetThread[] threads = new GetThread[urisToGet.length];
for (int i = 0; i < threads.length; i++) {
HttpGet httpget = new HttpGet(urisToGet[i]);
threads[i] = new GetThread(httpclient, httpget, i + 1);
}
// start the threads
for (int j = 0; j < threads.length; j++) {
threads[j].start();
}
// join the threads
for (int j = 0; j < threads.length; j++) {
threads[j].join();
}
} finally {
httpclient.close();
}
}
/**
* A thread that performs a GET.
*/
static class GetThread extends Thread {
private final CloseableHttpClient httpClient;
private final HttpContext context;
private final HttpGet httpget;
private final int id;
public GetThread(CloseableHttpClient httpClient, HttpGet httpget, int id) {
this.httpClient = httpClient;
this.context = new BasicHttpContext();
this.httpget = httpget;
this.id = id;
}
/**
* Executes the GetMethod and prints some status information.
*/
@Override
public void run() {
try {
System.out.println(id + " - about to get something from " + httpget.getURI());
CloseableHttpResponse response = httpClient.execute(httpget, context);
try {
System.out.println(id + " - get executed");
// get the response body as an array of bytes
HttpEntity entity = response.getEntity();
if (entity != null) {
byte[] bytes = EntityUtils.toByteArray(entity);
System.out.println(id + " - " + bytes.length + " bytes read");
}
} finally {
response.close();
}
} catch (Exception e) {
System.out.println(id + " - error: " + e);
}
}
}
}
