FLex调用servlet连接数据库

转载自（http://blog.csdn.net/pengpeng2395/article/details/4157421）

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

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, HttpServletResponse response)
            throws ServletException, 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,type,price,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

1. 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

1. dataProvider="{service.lastResult.products.product}"
   1. 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。
   2. 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。
   3. Product子标签和Flex中<mx:columns>的dataField属性相对应。

结果图

完整的JAVA和FLEX代码可以在这里下载