Android入门：用HttpClient模拟HTTP的GET和POST请求

一、HttpClient介绍

 

HttpClient是用来模拟HTTP请求的，其实实质就是把HTTP请求模拟后发给Web服务器；

 

Android已经集成了HttpClient，因此可以直接使用；

 

注：此处HttpClient代码不只可以适用于Android，也可适用于一般的Java程序；

 

HTTP GET核心代码：

 

(1)DefaultHttpClient client = new DefaultHttpClient();

(2)HttpGet get = new HttpGet(String url);//此处的URL为http://..../path?arg1=value&....argn=value

(3)HttpResponse response = client.execute(get); //模拟请求

(4)int code = response.getStatusLine().getStatusCode();//返回响应码

(5)InputStream in = response.getEntity().getContent();//服务器返回的数据

 

 

HTTP POST核心代码：

 

(1)DefaultHttpClient client = new DefaultHttpClient();

(2)BasicNameValuePair pair = new BasicNameValuePair(String name,String value);//创建一个请求头的字段，比如content-type,text/plain

(3)UrlEncodedFormEntity entity = new UrlEncodedFormEntity(List<NameValuePair> list,String encoding);//对自定义请求头进行URL编码

(4)HttpPost post = new HttpPost(String url);//此处的URL为http://..../path

(5)post.setEntity(entity);

(6)HttpResponse response = client.execute(post);

(7)int code = response.getStatusLine().getStatusCode();

(8)InputStream in = response.getEntity().getContent();//服务器返回的数据

 

二、服务器端代码

 

服务器端代码和通过URLConnection发出请求的代码不变：

 

1. package org.xiazdong.servlet;
2. import java.io.IOException;
3. import java.io.OutputStream;
4. import javax.servlet.ServletException;
5. import javax.servlet.annotation.WebServlet;
6. import javax.servlet.http.HttpServlet;
7. import javax.servlet.http.HttpServletRequest;
8. import javax.servlet.http.HttpServletResponse;
9. @WebServlet("/Servlet1")
10. public class Servlet1 extends HttpServlet {
11. protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
12. String nameParameter = request.getParameter("name");
13. String ageParameter = request.getParameter("age");
14. String name = new String(nameParameter.getBytes("ISO-8859-1"),"UTF-8");
15. String age = new String(ageParameter.getBytes("ISO-8859-1"),"UTF-8");
16. System.out.println("GET");
17. System.out.println("name="+name);
18. System.out.println("age="+age);
19. response.setCharacterEncoding("UTF-8");
20. OutputStream out = response.getOutputStream();//返回数据
21. out.write("GET请求成功!".getBytes("UTF-8"));
22. out.close();
23. }
24. protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
25. request.setCharacterEncoding("UTF-8");
26. String name = request.getParameter("name");
27. String age  = request.getParameter("age");
28. System.out.println("POST");
29. System.out.println("name="+name);
30. System.out.println("age="+age);
31. response.setCharacterEncoding("UTF-8");
32. OutputStream out = response.getOutputStream();
33. out.write("POST请求成功!".getBytes("UTF-8"));
34. out.close();
35. }
36. }

 

三、Android客户端代码

 

效果如下：

 

 

 

在AndroidManifest.xml加入：

1. <uses-permission android:name="android.permission.INTERNET"/>

 

MainActivity.java

 

1. package org.xiazdong.network.httpclient;
2. import java.io.ByteArrayOutputStream;
3. import java.io.IOException;
4. import java.io.InputStream;
5. import java.net.URLEncoder;
6. import java.util.ArrayList;
7. import java.util.List;
8. import org.apache.http.HttpResponse;
9. import org.apache.http.NameValuePair;
10. import org.apache.http.client.entity.UrlEncodedFormEntity;
11. import org.apache.http.client.methods.HttpGet;
12. import org.apache.http.client.methods.HttpPost;
13. import org.apache.http.impl.client.DefaultHttpClient;
14. import org.apache.http.message.BasicNameValuePair;
15. import android.app.Activity;
16. import android.os.Bundle;
17. import android.view.View;
18. import android.view.View.OnClickListener;
19. import android.widget.Button;
20. import android.widget.EditText;
21. import android.widget.Toast;
22. public class MainActivity extends Activity {
23. private EditText name, age;
24. private Button getbutton, postbutton;
25. private OnClickListener listener = new OnClickListener() {
26. @Override
27. public void onClick(View v) {
28. try{
29. if(postbutton==v){
30. /*
31. * NameValuePair代表一个HEADER，List<NameValuePair>存储全部的头字段
32. * UrlEncodedFormEntity类似于URLEncoder语句进行URL编码
33. * HttpPost类似于HTTP的POST请求
34. * client.execute()类似于发出请求，并返回Response
35. */
36. DefaultHttpClient client = new DefaultHttpClient();
37. List<NameValuePair> list = new ArrayList<NameValuePair>();
38. NameValuePair pair1 = new BasicNameValuePair("name", name.getText().toString());
39. NameValuePair pair2 = new BasicNameValuePair("age", age.getText().toString());
40. list.add(pair1);
41. list.add(pair2);
42. UrlEncodedFormEntity entity = new UrlEncodedFormEntity(list,"UTF-8");
43. HttpPost post = new HttpPost("http://192.168.0.103:8080/Server/Servlet1");
44. post.setEntity(entity);
45. HttpResponse response = client.execute(post);
46. if(response.getStatusLine().getStatusCode()==200){
47. InputStream in = response.getEntity().getContent();//接收服务器的数据，并在Toast上显示
48. String str = readString(in);
49. Toast.makeText(MainActivity.this, str, Toast.LENGTH_SHORT).show();
50. }
51. else Toast.makeText(MainActivity.this, "POST提交失败", Toast.LENGTH_SHORT).show();
52. }
53. if(getbutton==v){
54. DefaultHttpClient client = new DefaultHttpClient();
55. StringBuilder buf = new StringBuilder("http://192.168.0.103:8080/Server/Servlet1");
56. buf.append("?");
57. buf.append("name="+URLEncoder.encode(name.getText().toString(),"UTF-8")+"&");
58. buf.append("age="+URLEncoder.encode(age.getText().toString(),"UTF-8"));
59. HttpGet get = new HttpGet(buf.toString());
60. HttpResponse response = client.execute(get);
61. if(response.getStatusLine().getStatusCode()==200){
62. InputStream in = response.getEntity().getContent();
63. String str = readString(in);
64. Toast.makeText(MainActivity.this, str, Toast.LENGTH_SHORT).show();
65. }
66. else Toast.makeText(MainActivity.this, "GET提交失败", Toast.LENGTH_SHORT).show();
67. }
68. }
69. catch(Exception e){}
70. }
71. };
72. @Override
73. public void onCreate(Bundle savedInstanceState) {
74. super.onCreate(savedInstanceState);
75. setContentView(R.layout.main);
76. name = (EditText) this.findViewById(R.id.name);
77. age = (EditText) this.findViewById(R.id.age);
78. getbutton = (Button) this.findViewById(R.id.getbutton);
79. postbutton = (Button) this.findViewById(R.id.postbutton);
80. getbutton.setOnClickListener(listener);
81. postbutton.setOnClickListener(listener);
82. }
83. protected String readString(InputStream in) throws Exception {
84. byte[]data = new byte[1024];
85. int length = 0;
86. ByteArrayOutputStream bout = new ByteArrayOutputStream();
87. while((length=in.read(data))!=-1){
88. bout.write(data,0,length);
89. }
90. return new String(bout.toByteArray(),"UTF-8");
91. }
92. }