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FLex调用servlet连接数据库

前言

Flex 最重要的部分之一就是和服务器以及数据库的通讯。Flex 提供了三个类来与服务器通讯： HTTPService，RemoteObject 以及WebService。

HTTPService 类提供了使用超文本传输协议（HTTP）与服务器通讯的方式。一个Flex 应用程序可以使用GET 或者POST 请求来发送数据到一个服务器并且处理这个请求返回的 XML 或者字符串。使用HTTPService 类，你可以与PHP 页面,ColdFusion 页面，JavaServe页面（ jsp），Java servlet， Ruby onRails， 以及ASP 动态网页通讯。

与Java Servlet通讯

由于本人是Java出身，所以这里就来讨论一下与Servlet的通讯方式。

建立数据库

这里选用MySql数据库，首先建立如下的数据库表

写服务器端Java代码

Servlet

[java] view plain copy print ?

1. package?servlet;??
2. ??
3. import?java.io.IOException;??
4. import?java.io.PrintWriter;??
5. import?java.util.List;??
6. ??
7. import?javax.servlet.ServletException;??
8. import?javax.servlet.http.HttpServlet;??
9. import?javax.servlet.http.HttpServletRequest;??
10. import?javax.servlet.http.HttpServletResponse;??
11. ??
12. import?PODO.Product;??
13. import?db.ProductDao;??
14. ??
15. public?class?GetProductServlet?extends?HttpServlet?{??
16. ????List?result;??
17. ??
18. ????/**?
19. ?????*?Constructor?of?the?object.?
20. ?????*/??
21. ????public?GetProductServlet()?{??
22. ????????super();??
23. ????}??
24. ??
25. ????/**?
26. ?????*?Destruction?of?the?servlet.?<br>?
27. ?????*/??
28. ????public?void?destroy()?{??
29. ????????super.destroy();?//?Just?puts?"destroy"?string?in?log ??
30. ????????//?Put?your?code?here ??
31. ????}??
32. ??
33. ????/**?
34. ?????*?The?doGet?method?of?the?servlet.?<br>?
35. ?????*??
36. ?????*?This?method?is?called?when?a?form?has?its?tag?value?method?equals?to?get.?
37. ?????*??
38. ?????*?@param?request?
39. ?????*????????????the?request?send?by?the?client?to?the?server?
40. ?????*?@param?response?
41. ?????*????????????the?response?send?by?the?server?to?the?client?
42. ?????*?@throws?ServletException?
43. ?????*?????????????if?an?error?occurred?
44. ?????*?@throws?IOException?
45. ?????*?????????????if?an?error?occurred?
46. ?????*/??
47. ????public?void?doGet(HttpServletRequest?request,?HttpServletResponse?response)??
48. ????????????throws?ServletException,?IOException?{??
49. ????????result?=?new?ProductDao().getProduct();??
50. ????????String?xmlContent?=?"<?xml?version='1.0'?encoding='utf-8'?><products>";??
51. ????????response.setContentType("text/xml;charset=utf-8");??
52. ????????PrintWriter?out?=?response.getWriter();??
53. ????????if?(result?!=?null)?{??
54. ????????????for?(int?i?=?0;?i?<?result.size();?i++)?{??
55. ????????????????Product?p?=?(Product)?result.get(i);??
56. ????????????????xmlContent?+=?"<product><name>"?+?p.getName()?+?"</name><type>"??
57. ????????????????????????+?p.getType()?+?"</type><price>"?+?p.getPrice()??
58. ????????????????????????+?"</price><num>"?+?p.getNum()?+?"</num></product>";??
59. ????????????}??
60. ????????????xmlContent?+=?"</products>";??
61. ????????????out.print(xmlContent);??
62. ????????????out.flush();??
63. ????????????out.close();??
64. ????????}??
65. ??
66. ????}??
67. ??
68. ????/**?
69. ?????*?The?doPost?method?of?the?servlet.?<br>?
70. ?????*??
71. ?????*?This?method?is?called?when?a?form?has?its?tag?value?method?equals?to?
72. ?????*?post.?
73. ?????*??
74. ?????*?@param?request?
75. ?????*????????????the?request?send?by?the?client?to?the?server?
76. ?????*?@param?response?
77. ?????*????????????the?response?send?by?the?server?to?the?client?
78. ?????*?@throws?ServletException?
79. ?????*?????????????if?an?error?occurred?
80. ?????*?@throws?IOException?
81. ?????*?????????????if?an?error?occurred?
82. ?????*/??
83. ????public?void?doPost(HttpServletRequest?request,?IOException?{??
84. ??
85. ????????this.doGet(request,?response);??
86. ????}??
87. ??
88. ????/**?
89. ?????*?Initialization?of?the?servlet.?<br>?
90. ?????*??
91. ?????*?@throws?ServletException?
92. ?????*?????????????if?an?error?occurs?
93. ?????*/??
94. ????public?void?init()?throws?ServletException?{??
95. ????????//?Put?your?code?here ??
96. ????}??
97. }??

package servlet;import java.io.IOException;import java.io.PrintWriter;import java.util.List;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import PODO.Product;import db.ProductDao;public class GetProductServlet extends HttpServlet { List result; /** * Constructor of the object. */ public GetProductServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request * the request send by the client to the server * @param response * the response send by the server to the client * @throws ServletException * if an error occurred * @throws IOException * if an error occurred */ public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { result = new ProductDao().getProduct(); String xmlContent = "<?xml version='1.0' encoding='utf-8'?><products>"; response.setContentType("text/xml;charset=utf-8"); PrintWriter out = response.getWriter(); if (result != null) { for (int i = 0; i < result.size(); i++) { Product p = (Product) result.get(i); xmlContent += "<product><name>" + p.getName() + "</name><type>" + p.getType() + "</type><price>" + p.getPrice() + "</price><num>" + p.getNum() + "</num></product>"; } xmlContent += "</products>"; out.print(xmlContent); out.flush(); out.close(); } } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to * post. * * @param request * the request send by the client to the server * @param response * the response send by the server to the client * @throws ServletException * if an error occurred * @throws IOException * if an error occurred */ public void doPost(HttpServletRequest request,IOException { this.doGet(request,response); } /** * Initialization of the servlet. <br> * * @throws ServletException * if an error occurs */ public void init() throws ServletException { // Put your code here }}

数据库连接

public class MyConnection { public Connection conn = null; public MyConnection() { try { // 注册数据库驱动程序为MYSQL驱动 Class.forName("com.mysql.jdbc.Driver"); } catch (java.lang.ClassNotFoundException e) { System.err.println("mydb(): " + e.getMessage()); } try { conn = DriverManager.getConnection( "jdbc:mysql://127.0.0.1:3306/flex","root","root"); } catch (SQLException ex) { System.err.println("conn:" + ex.getMessage()); } } public Connection getDbConnection() { return conn; }}

?

DAO

public class ProductDao { Connection conn; ResultSet rs; Statement stmt; public ProductDao() { conn = new MyConnection().getDbConnection(); try { stmt = conn.createStatement(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public List getProduct() { List list = new ArrayList(); try { String sql = "select * from product"; rs = stmt.executeQuery(sql); while (rs.next()) { String name=rs.getString("name"); String type=rs.getString("type"); double price=Double.parseDouble(rs.getString("price")); int num=Integer.parseInt(rs.getString("num")); Product p=new Product(name,num); list.add(p); } rs.close(); stmt.close(); conn.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { return list; } }}

?

PODO

public class Product { private String name; private String type; private double price; private int num; public Product(String name,String type,double price,int num) { this.name = name; this.type = type; this.price = price; this.num = num; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getType() { return type; } public void setType(String type) { this.type = type; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } public int getNum() { return num; } public void setNum(int num) { this.num = num; }}

?

部署TOMCAT

这一部分略过，如果觉得手动部署比较麻烦，我们可以使用MyEclipse插件。值得注意的是web.xml文件的配置，一定要正确配置servlet,下面我给出正确示例

<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <display-name>Benson</display-name> <servlet> <description>This is the description </description> <display-name>This is the display name </display-name> <servlet-name>GetProductServlet</servlet-name> <servlet-class>servlet.GetProductServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>GetProductServlet</servlet-name> <url-pattern>/servlet/GetProductServlet</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <login-config> <auth-method>BASIC</auth-method> </login-config></web-app>

编写FLEX MXML

<?xml version="1.0" encoding="utf-8"?><mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" creationComplete="send()"> <mx:HTTPService id="service" url="http://localhost:8080/servlet/servlet/GetProductServlet" method="GET" /> <mx:Script> <!--[CDATA[ private function send():void{ //发送请求 service.send(); } ]]--> </mx:Script> <mx:Canvas x="0" y="0" width="100%" height="100%"> <mx:DataGrid x="0" y="68" width="676" height="383" id="productdata" dataProvider="{service.lastResult.products.product}" fontFamily="Times New Roman" fontSize="16"> <mx:columns> <mx:DataGridColumn headerText="商品名称" dataField="name"/> <mx:DataGridColumn headerText="商品类别" dataField="type"/> <mx:DataGridColumn headerText="商品价格" dataField="price"/> <mx:DataGridColumn headerText="剩余数量" dataField="num"/> </mx:columns> </mx:DataGrid> <mx:ApplicationControlBar x="0" y="0" height="70" width="676"> </mx:ApplicationControlBar> </mx:Canvas></mx:Application>

?

代码重点解释

1.?????? creationComplete="send()"

表明当这个Flex应用创建完成时，就发送这个HttpServer请求给Servlet

2.?????url=http://localhost:8080/servlet/servlet/GetProductServlet

第一个servlet是我们服务器端的工程名

第二个servelt是servlet所在包名

GetProductServlet使我们真正的servlet名称

3.?????? dataProvider="{service.lastResult.products.product}"

a.?lastResult：在做了一个呼叫到一个HTTPService 之后，数据会从服务返回，并被放置到服务组件所包含的lastResult 对象。

b.?由于我们返回的是一个XML数据，所以service.lastResult.products.product就代表返回XML中products标签下的所有product标签内容。

c.? Product子标签和Flex中<mx:columns>的dataField属性相对应。

结果图

?