Servlet读取xml文件的配置参数

Posted 2020-12-24 biaogejiushibiao

web.xml中数据库连接配置：

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 3 xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
 4 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
 5 id="WebApp_ID" version="2.5">
 6 <display-name>Servelt_ReadingDBFromWebXml</display-name>
 7 <welcome-file-list>
 8    <welcome-file>index.html</welcome-file>
 9    <welcome-file>index.htm</welcome-file>
10    <welcome-file>index.jsp</welcome-file>
11    <welcome-file>default.html</welcome-file>
12    <welcome-file>default.htm</welcome-file>
13    <welcome-file>default.jsp</welcome-file>
14 </welcome-file-list>

web.xml

 

<!-- 通过getServletContext().getInitParameter("XX")读取 -->
<context-param>
   <param-name>driver</param-name>
   <param-value>com.mysql.jdbc.Driver</param-value>
</context-param>

<context-param>
   <param-name>url</param-name>
   <param-value>jdbc:mysql://localhost:3306/sample</param-value>
</context-param>

<context-param>
   <param-name>username</param-name>
   <param-value>root</param-value>
</context-param>

<context-param>
   <param-name>password</param-name>
   <param-value>admin</param-value>
</context-param>

<servlet>
   <servlet-name>DBServlet</servlet-name>
   <servlet-class>demo.DBServlet</servlet-class>

   <!-- 通过getServletConfig().getInitParameter("XX")读取 -->
   <init-param>
    <param-name>driver</param-name>
    <param-value>com.mysql.jdbc.Driver</param-value>
   </init-param>
   <init-param>
    <param-name>url</param-name>
    <param-value>jdbc:mysql://localhost:3306/sample</param-value>
   </init-param>
   <init-param>
    <param-name>username</param-name>
    <param-value>root</param-value>
   </init-param>
   <init-param>
    <param-name>password</param-name>
    <param-value>admin</param-value>
   </init-param>

</servlet>

<servlet-mapping>
   <servlet-name>DBServlet</servlet-name>
   <url-pattern>/readingDB</url-pattern>
</servlet-mapping>
</web-app>

Servlet代码：

 1 /**
 2 * 
 3 */
 4 package demo;
 5 
 6 import java.io.IOException;
 7 import java.io.PrintWriter;
 8 import java.sql.Connection;
 9 import java.sql.DriverManager;
10 import java.sql.PreparedStatement;
11 import java.sql.ResultSet;
12 import java.sql.SQLException;
13 
14 import javax.servlet.ServletException;
15 import javax.servlet.http.HttpServlet;
16 import javax.servlet.http.HttpServletRequest;
17 import javax.servlet.http.HttpServletResponse;
18 
19 /**
20 * Reading DB Config from web.xml
21 */
22 public class DBServlet extends HttpServlet {
23 
24 /**
25 * 
26 */
27 private static final long serialVersionUID = 1L;
28 
29 private String diverClass;
30 private String userName;
31 private String password;
32 private String url;
33 
34 @Override
35 public void init() throws ServletException {
36    diverClass = /* getServletConfig(). */getServletContext().getInitParameter("driver");
37    userName = /* getServletConfig(). */getServletContext().getInitParameter("username");
38    password = /* getServletConfig(). */getServletContext().getInitParameter("password");
39    url = /* getServletConfig(). */getServletContext().getInitParameter("url");
40 
41    try {
42     Class.forName(diverClass);
43    } catch (Exception e) {
44     e.printStackTrace();
45    }
46 
47 }
48 
49 @Override
50 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
51    Connection connection = null;
52    PreparedStatement statement = null;
53 
54    try {
55     connection = DriverManager.getConnection(url, userName, password);
56     statement = connection.prepareStatement("select * from customer");
57     ResultSet rs = statement.executeQuery();
58 
59     PrintWriter printWriter = resp.getWriter();
60     while (rs.next()) {
61      printWriter.println(rs.getString("id"));
62      printWriter.println(rs.getString("name"));
63     }
64    } catch (SQLException e) {
65     e.printStackTrace();
66    } finally {
67     try {
68      if (statement != null) {
69       statement.close();
70      }
71 
72      if (connection != null) {
73       connection.close();
74      }
75     } catch (SQLException e) {
76      e.printStackTrace();
77     }
78    }
79 }
80 }

Servlet

 

原文链接：https://www.cnblogs.com/ilahsa/archive/2012/09/29/2708460.html