1.使用java.net.URL类访问网络数据
时间：2019-07-09 09:51:01
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[导读]和网络打交道总是难免的，所以很有必要学一下怎么操作和网络交互。我们通过URL类或者HttpClient类，都可以对网络访问，至于这两个类的区别，HttpClient类底层还是使用了Url类，对其封装了
和网络打交道总是难免的，所以很有必要学一下怎么操作和网络交互。
我们通过URL类或者HttpClient类，都可以对网络访问，至于这两个类的区别，HttpClient类底层还是使用了Url类，对其封装了一下。
第一步：建立一个服务器端，其中get方法返回"you had receied the message from http://192.168.1.132:8088/WebServer/student.do”;post方法返回输入的name。
package org.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class StudentAction extends HttpServlet {
private static final long serialVersionUID = 1L;
public StudentAction() {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.write("you had receied the message from http://192.168.1.132:8088/WebServer/student.do");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
String name = request.getParameter("name");
PrintWriter out = response.getWriter();
out.write(name);
}
}第二步:新建android projiect，新建一个java类，这里首先使用URL类，代码如下：
其中添加一个get方法：
package org.example.httpclient;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class MHttpClient {
public void get() throws Exception {
// 实例化一个URL对象
URL url = new URL("http://192.168.1.132:8088/WebServer/student.do");
// 打开连接
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
// 设置访问超时时间
conn.setConnectTimeout(5 * 1000);
// 设置请求参数
conn.setRequestMethod("GET");
// 得到输入流
InputStream in = conn.getInputStream();
// 从输入流中读取内容放到内存中
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while ((len = in.read(buffer)) != -1) {
out.write(buffer, 0, len);
}
System.out.println(new String(out.toByteArray()));
out.close();
in.close();
}
}我们使用单元测试，在manifest.xml里添加
别忘了加入internet访问权限，否则就会报java.net.UnknownHostException的错误。
接下来新建一个MHttpclientTestCase类,需要继承AndroidTestCase类
添加一个测试方法：
public void testGet() throws Exception {
MHttpClient url = new MHttpClient();
url.get();
}
然后在该文件右键->run as->android JUnit Test
可以在logcat中看到返回的信息“you had receied the message from http://192.168.1.132:8088/WebServer/student.do”。
如果要在请求中带参数的话，直接把参数附加到请求路径的后面就可以了,比如：http://www.baidu.com/s?wd=1&rsv_bp=0&rsv_spt=3&inputT=576
接下来，我们使用post请求。再MHttpClient类中建一个方法：
public void post() throws Exception {
String postData = "name=11";
// 实例化一个URL对象
URL url = new URL("http://192.168.1.132:8088/WebServer/student.do");
// 打开连接
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
// 设置访问超时时间
conn.setReadTimeout(5 * 1000);
// 设置请求方式
conn.setRequestMethod("POST");
// 发送POST请求必须设置允许输出
conn.setDoOutput(true);
conn.setRequestProperty("Charset", "utf-8");
conn.setRequestProperty("Content-Length", postData.length() + "");
OutputStream out = conn.getOutputStream();
out.write(postData.getBytes());
out.flush();
if (conn.getResponseCode() == 200) {
InputStream in = conn.getInputStream();
// 从输入流中读取内容放到内存中
ByteArrayOutputStream out2 = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while ((len = in.read(buffer)) != -1) {
out2.write(buffer, 0, len);
}
System.out.println(new String(out2.toByteArray()));
out2.close();
in.close();
}
out.close();
}
在单元测试类MHttpclientTestCase再添加一个方法：
public void testPost() throws Exception {
MHttpClient url = new MHttpClient();
url.post();
}在方法名称右键->run as->android JUnit Test
可在logcat里看到返回结果 “11”
贴上全部代码：
MHttpClient.java
package org.example.httpclient;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class MHttpClient {
public void get() throws Exception {
// 实例化一个URL对象
URL url = new URL("http://192.168.1.132:8088/WebServer/student.do");
// 打开连接
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
// 设置访问超时时间
conn.setConnectTimeout(5 * 1000);
// 设置请求方式
conn.setRequestMethod("GET");
// 得到输入流
InputStream in = conn.getInputStream();
// 从输入流中读取内容放到内存中
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while ((len = in.read(buffer)) != -1) {
out.write(buffer, 0, len);
}
System.out.println(new String(out.toByteArray()));
out.close();
in.close();
}
public void post() throws Exception {
String postData = "name=11";
byte[] data = postData.getBytes();
// 实例化一个URL对象
URL url = new URL("http://192.168.1.132:8088/WebServer/student.do");
// 打开连接
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
// 设置访问超时时间
conn.setConnectTimeout(10 * 1000);
// 设置请求方式
conn.setRequestMethod("POST");
// 发送POST请求必须设置允许输出
conn.setDoOutput(true);
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("Content-Length", data.length + "");
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
conn.setRequestProperty("Connection", "Keep-Alive");// 维持长连接
OutputStream out = conn.getOutputStream();
out.write(data);
out.flush();
if (conn.getResponseCode() == 200) {
InputStream in = conn.getInputStream();
// 从输入流中读取内容放到内存中
ByteArrayOutputStream out2 = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while ((len = in.read(buffer)) != -1) {
out2.write(buffer, 0, len);
}
System.out.println(new String(out2.toByteArray()));
out2.close();
in.close();
}
out.close();
}
}
MHttpclientTestCase.java
package org.example.httpclient;
import android.test.AndroidTestCase;
public class MHttpclientTestCase extends AndroidTestCase {
public void testGet() throws Exception {
MHttpClient url = new MHttpClient();
url.get();
}
public void testPost() throws Exception {
MHttpClient url = new MHttpClient();
url.post();
}
}
AndroidManifest.xml
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