Question

HttpURLConnection 怎样取页面使用dwr显示的数据？求高手帮助！

Answer 1

HttpURLConnection为javaAPI提供的一种Rest访问的方式。其支持对Post,Delete,Get,Put等方式的访问。

以下为对于HttpURLConnection对Post等方式访问的一段代码。

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1. package com.sw.study.urlConnection;
2.
3. import java.io.BufferedReader;
4. import java.io.InputStreamReader;
5. import java.io.OutputStream;
6. import java.net.HttpURLConnection;
7. import java.net.URL;
8. import java.net.URLConnection;
9. import java.util.HashMap;
10. import java.util.Map;
11.
12. public class URLConnectionUtil {
13.
14. private static final String SERVLET_POST = "POST" ;
15. private static final String SERVLET_GET = "GET" ;
16. private static final String SERVLET_DELETE = "DELETE" ;
17. private static final String SERVLET_PUT = "PUT" ;
18.
19. private static String prepareParam(Map<String,Object> paramMap){
20. StringBuffer sb = new StringBuffer();
21. if(paramMap.isEmpty()){
22. return "" ;
23. }else{
24. for(String key: paramMap.keySet()){
25. String value = (String)paramMap.get(key);
26. if(sb.length()<1){
27. sb.append(key).append("=").append(value);
28. }else{
29. sb.append("&").append(key).append("=").append(value);
30. }
31. }
32. return sb.toString();
33. }
34. }
35.
36. public static void doPost(String urlStr,Map<String,Object> paramMap ) throws Exception{
37. URL url = new URL(urlStr);
38. HttpURLConnection conn = (HttpURLConnection)url.openConnection();
39. conn.setRequestMethod(SERVLET_POST);
40. String paramStr = prepareParam(paramMap);
41. conn.setDoInput(true);
42. conn.setDoOutput(true);
43. OutputStream os = conn.getOutputStream();
44. os.write(paramStr.toString().getBytes("utf-8"));
45. os.close();
46.
47. BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
48. String line ;
49. String result ="";
50. while( (line =br.readLine()) != null ){
51. result += "\n"+line;
52. }
53. System.out.println(result);
54. br.close();
55.
56. }
57.
58. public static void doGet(String urlStr,Map<String,Object> paramMap ) throws Exception{
59. String paramStr = prepareParam(paramMap);
60. if(paramStr == null || paramStr.trim().length()<1){
61.
62. }else{
63. urlStr +="?"+paramStr;
64. }
65. System.out.println(urlStr);
66. URL url = new URL(urlStr);
67. HttpURLConnection conn = (HttpURLConnection)url.openConnection();
68. conn.setRequestMethod(SERVLET_PUT);
69. conn.setRequestProperty("Content-Type","text/html; charset=UTF-8");
70.
71. conn.connect();
72. BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
73. String line ;
74. String result ="";
75. while( (line =br.readLine()) != null ){
76. result += "\n"+line;
77. }
78. System.out.println(result);
79. br.close();
80. }
81.
82. public static void doPut(String urlStr,Map<String,Object> paramMap) throws Exception{
83. URL url = new URL(urlStr);
84. HttpURLConnection conn = (HttpURLConnection)url.openConnection();
85. conn.setRequestMethod(SERVLET_PUT);
86. String paramStr = prepareParam(paramMap);
87. conn.setDoInput(true);
88. conn.setDoOutput(true);
89. OutputStream os = conn.getOutputStream();
90. os.write(paramStr.toString().getBytes("utf-8"));
91. os.close();
92.
93. BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
94. String line ;
95. String result ="";
96. while( (line =br.readLine()) != null ){
97. result += "\n"+line;
98. }
99. System.out.println(result);
100. br.close();
101.
102. }
103.
104. public static void doDelete(String urlStr,Map<String,Object> paramMap) throws Exception{
105. String paramStr = prepareParam(paramMap);
106. if(paramStr == null || paramStr.trim().length()<1){
107.
108. }else{
109. urlStr +="?"+paramStr;
110. }
111. System.out.println(urlStr);
112. URL url = new URL(urlStr);
113. HttpURLConnection conn = (HttpURLConnection)url.openConnection();
114. conn.setDoOutput(true);
115. conn.setRequestMethod(SERVLET_DELETE);
116. //屏蔽掉的代码是错误的，java.net.ProtocolException: HTTP method DELETE doesn't support output
117. /* OutputStream os = conn.getOutputStream();
118. os.write(paramStr.toString().getBytes("utf-8"));
119. os.close(); */
120.
121. if(conn.getResponseCode() ==200){
122. System.out.println("成功");
123. }else{
124. System.out.println(conn.getResponseCode());
125. }
126. }
127.
128. public static void main(String[] args) throws Exception{
129. String urlStr = "http://localhost:8080/SwTest/ReceiveDataServlet";
130. Map<String,Object> map = new HashMap<String,Object>();
131. map.put("username","张三");
132. map.put("password","88888");
133. // URLConnectionUtil.doGet(urlStr, map);
134. // URLConnectionUtil.doPost(urlStr, map);
135. // URLConnectionUtil.doPut(urlStr, map);
136. URLConnectionUtil.doDelete(urlStr, map);
137.
138. }
139.
140.
141. }

方法中是存在重复的。有些方法是可以通过参数的改变来达到统一，但是那样的做法对于程序的扩展性会有很大的局限性。

还是对于每一种方式提供一个单独的方法进行访问比较好。

在Servlet端，获取参数可以通过

request.getInputStream,及request.getParamter来进行。

其中，当Rest访问传入参数是通过conn的outputStream来进行的，可以通过request.getInputStream来进行参数获取（Post方式可通用）；

当以url?key=value方法传递参数时，可以通过request.getParamter来进行参数获取。（Post方式可通用）

其中request.getInputStream和request.getParamter两种方式不能同时出现。当request.getParamter运行的过程，也是输入流的读取过程。当输入流读取完成后，再次调用时无效的。

附上Servlet端程序

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1. package com.sw.servlet;
2.
3. import java.io.BufferedReader;
4. import java.io.IOException;
5. import java.io.InputStreamReader;
6. import java.io.OutputStream;
7.
8. import javax.servlet.ServletException;
9. import javax.servlet.ServletInputStream;
10. import javax.servlet.http.HttpServlet;
11. import javax.servlet.http.HttpServletRequest;
12. import javax.servlet.http.HttpServletResponse;
13.
14. /**
15. * Servlet implementation class ReceiveDataServlet
16. */
17. public class ReceiveDataServlet extends HttpServlet {
18. private static final long serialVersionUID = 1L;
19.
20. /**
21. * @see HttpServlet#HttpServlet()
22. */
23. public ReceiveDataServlet() {
24. super();
25. // TODO Auto-generated constructor stub
26. }
27.
28. /**
29. * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
30. */
31. protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
32. System.out.println("----------get--------------");
33. String username = new String(request.getParameter("username").getBytes("iso-8859-1"),"utf-8");
34. String password = new String(request.getParameter("password").getBytes("iso-8859-1"),"utf-8");
35. System.out.println(username);
36. System.out.println(password);
37. OutputStream os = response.getOutputStream();
38. os.write("get".getBytes("utf-8"));
39. }
40.
41. /**
42. * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
43. */
44. protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
45. System.out.println("----------post--------------");
46. BufferedReader br = new BufferedReader(new InputStreamReader((ServletInputStream)request.getInputStream()));
47. String line = null;
48. StringBuilder sb = new StringBuilder();
49. while((line = br.readLine())!=null){
50. sb.append(line);
51. }
52. System.out.println(sb.toString());
53. br.close();
54. /* String username = new String(request.getParameter("username").getBytes("iso-8859-1"),"utf-8");
55. String password = new String(request.getParameter("password").getBytes("iso-8859-1"),"utf-8");
56. System.out.println(username);
57. System.out.println(password);
58. */ OutputStream os = response.getOutputStream();
59. os.write("post".getBytes("utf-8"));
60. }
61.
62. @Override
63. protected void doDelete(HttpServletRequest request, HttpServletResponse response)
64. throws ServletException, IOException {
65. System.out.println("----------delete--------------");
66. String username = new String(request.getParameter("username").getBytes("iso-8859-1"),"utf-8");
67. String password = new String(request.getParameter("password").getBytes("iso-8859-1"),"utf-8");
68. System.out.println(username);
69. System.out.println(password);
70. OutputStream os = response.getOutputStream();
71. os.write("delete".getBytes("utf-8"));
72. }
73.
74. @Override
75. protected void doPut(HttpServletRequest request, HttpServletResponse response)
76. throws ServletException, IOException {
77. System.out.println("----------put--------------");
78.
79. /* BufferedReader br = new BufferedReader(new InputStreamReader((ServletInputStream)request.getInputStream()));
80. String line = null;
81. StringBuilder sb = new StringBuilder();
82. while((line = br.readLine())!=null){
83. sb.append(line);
84. }
85. System.out.println(sb.toString());
86. br.close();*/
87.
88. String username = new String(request.getParameter("username").getBytes("iso-8859-1"),"utf-8");
89. String password = new String(request.getParameter("password").getBytes("iso-8859-1"),"utf-8");
90. System.out.println(username);
91. System.out.println(password);
92. OutputStream os = response.getOutputStream();
93. os.write("put".getBytes("utf-8"));
94. }
95.
96. }

程序中对于request.getInputStream和getParameter的获取方式可能说明的会多少有些问题，我也是通过几组测试后得出的结论。肯定有我没有测试到得。如果有问题，请指出，我会再看到评论后进行测试，修改。

另外，Apache的HttpClient非常好。封装的详细。在我的工作中也用到过，在以后会对于HttpClient进行有些单独的程序笔记。

这里HttpUrlConnection是同事在别的项目中用到的，用法比较简单，我大体给他简单讲解了一下，简明扼要，功能完备，还是很方便，

所以在这里记下来，留个笔记吧。

btw,最近工作比较忙，有2个月没有写些东西了，在工作中确实还遇到了不少有意思的问题，最近刚好快闲下来了，慢慢整理一下。