这篇文章主要描述如何通过程序来访问网页内容，这是访问REST服务的基础。
在Java中，我们可以使用HttpUrlConnection类来实现，代码如下。
package http.base; import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.Charset;
import java.util.Map;
import java.util.Vector; public class HttpRequester {
private String defaultContentEncoding; public HttpRequester() {
this.defaultContentEncoding = Charset.defaultCharset().name();
} public HttpResponse sendGet(String urlString) throws IOException {
return this.send(urlString, "GET", null, null);
} public HttpResponse sendGet(String urlString, Map<String, String> params)
throws IOException {
return this.send(urlString, "GET", params, null);
} public HttpResponse sendGet(String urlString, Map<String, String> params,
Map<String, String> propertys) throws IOException {
return this.send(urlString, "GET", params, propertys);
} public HttpResponse sendPost(String urlString) throws IOException {
return this.send(urlString, "POST", null, null);
} public HttpResponse sendPost(String urlString, Map<String, String> params)
throws IOException {
return this.send(urlString, "POST", params, null);
} public HttpResponse sendPost(String urlString, Map<String, String> params,
Map<String, String> propertys) throws IOException {
return this.send(urlString, "POST", params, propertys);
} private HttpResponse send(String urlString, String method,
Map<String, String> parameters, Map<String, String> propertys)
throws IOException {
HttpURLConnection urlConnection = null; if (method.equalsIgnoreCase("GET") && parameters != null) {
StringBuffer param = new StringBuffer();
int i = 0;
for (String key : parameters.keySet()) {
if (i == 0)
param.append("?");
else
param.append("&");
param.append(key).append("=").append(parameters.get(key));
i++;
}
urlString += param;
}
URL url = new URL(urlString);
urlConnection = (HttpURLConnection) url.openConnection(); urlConnection.setRequestMethod(method);
urlConnection.setDoOutput(true);
urlConnection.setDoInput(true);
urlConnection.setUseCaches(false); if (propertys != null)
for (String key : propertys.keySet()) {
urlConnection.addRequestProperty(key, propertys.get(key));
} if (method.equalsIgnoreCase("POST") && parameters != null) {
StringBuffer param = new StringBuffer();
for (String key : parameters.keySet()) {
param.append("&");
param.append(key).append("=").append(parameters.get(key));
}
urlConnection.getOutputStream().write(param.toString().getBytes());
urlConnection.getOutputStream().flush();
urlConnection.getOutputStream().close();
} return this.makeContent(urlString, urlConnection);
} private HttpResponse makeContent(String urlString,
HttpURLConnection urlConnection) throws IOException {
HttpResponse httpResponser = new HttpResponse();
try {
InputStream in = urlConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(
new InputStreamReader(in));
httpResponser.contentCollection = new Vector<String>();
StringBuffer temp = new StringBuffer();
String line = bufferedReader.readLine();
while (line != null) {
httpResponser.contentCollection.add(line);
temp.append(line).append("/r/n");
line = bufferedReader.readLine();
}
bufferedReader.close(); String ecod = urlConnection.getContentEncoding();
if (ecod == null)
ecod = this.defaultContentEncoding; httpResponser.urlString = urlString; httpResponser.defaultPort = urlConnection.getURL().getDefaultPort();
httpResponser.file = urlConnection.getURL().getFile();
httpResponser.host = urlConnection.getURL().getHost();
httpResponser.path = urlConnection.getURL().getPath();
httpResponser.port = urlConnection.getURL().getPort();
httpResponser.protocol = urlConnection.getURL().getProtocol();
httpResponser.query = urlConnection.getURL().getQuery();
httpResponser.ref = urlConnection.getURL().getRef();
httpResponser.userInfo = urlConnection.getURL().getUserInfo(); httpResponser.content = new String(temp.toString().getBytes(), ecod);
httpResponser.contentEncoding = ecod;
httpResponser.code = urlConnection.getResponseCode();
httpResponser.message = urlConnection.getResponseMessage();
httpResponser.contentType = urlConnection.getContentType();
httpResponser.method = urlConnection.getRequestMethod();
httpResponser.connectTimeout = urlConnection.getConnectTimeout();
httpResponser.readTimeout = urlConnection.getReadTimeout(); return httpResponser;
} catch (IOException e) {
throw e;
} finally {
if (urlConnection != null)
urlConnection.disconnect();
}
} public String getDefaultContentEncoding() {
return this.defaultContentEncoding;
} public void setDefaultContentEncoding(String defaultContentEncoding) {
this.defaultContentEncoding = defaultContentEncoding;
}
}
HttpRequest类
package http.base;
import java.util.Vector;
public class HttpResponse {
String urlString;
int defaultPort;
String file;
String host;
String path;
int port;
String protocol;
String query;
String ref;
String userInfo;
String contentEncoding;
String content;
String contentType;
int code;
String message;
String method;
int connectTimeout;
int readTimeout;
Vector<String> contentCollection;
public String getContent() {
return content;
}
public String getContentType() {
return contentType;
}
public int getCode() {
return code;
}
public String getMessage() {
return message;
}
public Vector<String> getContentCollection() {
return contentCollection;
}
public String getContentEncoding() {
return contentEncoding;
}
public String getMethod() {
return method;
}
public int getConnectTimeout() {
return connectTimeout;
}
public int getReadTimeout() {
return readTimeout;
}
public String getUrlString() {
return urlString;
}
public int getDefaultPort() {
return defaultPort;
}
public String getFile() {
return file;
}
public String getHost() {
return host;
}
public String getPath() {
return path;
}
public int getPort() {
return port;
}
public String getProtocol() {
return protocol;
}
public String getQuery() {
return query;
}
public String getRef() {
return ref;
}
public String getUserInfo() {
return userInfo;
}
}
HttpResponse类
下面是一个简单的测试类。
package http.base;
public class HttpTest {
public static void main(String[] args) {
try {
HttpRequester request = new HttpRequester();
HttpResponse hr = request.sendGet("http://www.baidu.com");
System.out.println(hr.getUrlString());
System.out.println(hr.getProtocol());
System.out.println(hr.getHost());
System.out.println(hr.getPort());
System.out.println(hr.getContentEncoding());
System.out.println(hr.getMethod());
System.out.println(hr.getContent());
} catch (Exception e) {
e.printStackTrace();
}
}
}
因为REST服务的返回值一般都是JSON对象，下一篇文章中，我们来看Java对象和JSON之间如何转换。