Java_HttpClient获取返回类型为JSON或XML的数据
HttpClient 获取返回类型为JSON或XML的数据
使用httpcomponents-client-4.1.3（下载页面：http://hc.apache.org/httpcomponents-client-ga/download.html 最新是5.20发布的4.2版本）向网页发送HTTP请求抓取数据。
我所调用的服务明确写了他们支持多种类型的返回结果，如下：
The content types we currently support are:
•«text/html»
•«application/xhtml+xml»
•«text/xml»
•«application/json»
若不设置返回类型，每次获取的返回的内容是默认的text/html，而我需要的是更具有信息量的xml或者json。找了很多地方，没有看到设置ContentType的，纠结了一下。。。
其实，最好的教程还是httpclient下载下来自带的例子和pdf，其中examples中就有一个ClientGZipContentCompression.java，它是用来请求获取gzip的数据并解压显示。这个文件稍微改改就可以了。如下是接收json类型。
/ * ==================================================================== */
import java.io.IOException;
import java.io.InputStream;
import java.util.zip.GZIPInputStream;
import org.apache.http.Header;
import org.apache.http.HeaderElement;
import org.apache.http.HttpEntity;
import org.apache.http.HttpException;
import org.apache.http.HttpRequest;
import org.apache.http.HttpRequestInterceptor;
import org.apache.http.HttpResponse;
import org.apache.http.HttpResponseInterceptor;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.entity.HttpEntityWrapper;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.protocol.HttpContext;
import org.apache.http.util.EntityUtils;
public class JsonTest{
public final static void main(String[] args) throws Exception {
DefaultHttpClient httpclient = new DefaultHttpClient();
try {
httpclient.addRequestInterceptor(new HttpRequestInterceptor() {
public void process(
final HttpRequest request,
final HttpContext context) throws HttpException, IOException {
if (!request.containsHeader("Accept-Encoding")) {
request.addHeader("Accept", "application/json");
}
}
});
// httpclient.addResponseInterceptor(new HttpResponseInterceptor() {
//
// public void process(
// final HttpResponse response,
// final HttpContext context) throws HttpException, IOException {
// HttpEntity entity = response.getEntity();
// Header ceheader = entity.getContentEncoding();
// if (ceheader != null) {
// HeaderElement[] codecs = ceheader.getElements();
// for (int i = 0; i < codecs.length; i++) {
// if (codecs[i].getName().equalsIgnoreCase("gzip")) {
// response.setEntity(
// new GzipDecompressingEntity(response.getEntity()));
// return;
// }
// }
// }
// }
//
// });
HttpGet httpget = new HttpGet("http://your_url");
// Execute HTTP request
System.out.println("executing request " + httpget.getURI());
HttpResponse response = httpclient.execute(httpget);
System.out.println("----------------------------------------");
System.out.println(response.getStatusLine());
// System.out.println(response.getLastHeader("Content-Encoding"));
// System.out.println(response.getLastHeader("Content-Length"));
System.out.println("----------------------------------------");
HttpEntity entity = response.getEntity();
if (entity != null) {
String content = EntityUtils.toString(entity);
System.out.println(content);
System.out.println("----------------------------------------");
// System.out.println("Uncompressed size: "+content.length());
}
} finally {
// When HttpClient instance is no longer needed,
// shut down the connection manager to ensure
// immediate deallocation of all system resources
httpclient.getConnectionManager().shutdown();
}
}
// static class GzipDecompressingEntity extends HttpEntityWrapper {
//
// public GzipDecompressingEntity(final HttpEntity entity) {
// super(entity);
// }
//
// @Override
// public InputStream getContent()
// throws IOException, IllegalStateException {
//
// // the wrapped entity's getContent() decides about repeatability
// InputStream wrappedin = wrappedEntity.getContent();
//
// return new GZIPInputStream(wrappedin);
// }
//
// @Override
// public long getContentLength() {
// // length of ungzipped content is not known
// return -1;
// }
//
// }
}