java - Java中通过web.xml加载项目时如何调用属性文件？

Question

我已经制作了一个属性文件并仅从该文件加载我的数据库连接。我正在做的是使用 Servlet 上下文，我正在获取资源我在登录页面 (login.jsp) 中编写了这样的代码

    <%ServletContext servletContext = getServletContext();
InputStream input = getServletContext().getResourceAsStream("/WEB-INF/db.properties");
 if (input != null) {
     InputStreamReader isr = new InputStreamReader(input);
     BufferedReader reader = new BufferedReader(isr);
     PrintWriter writer = response.getWriter();
     String text;
     while ((text = reader.readLine()) != null) {
/*      System.out.println(text + "\n"); */
         servletContext.setAttribute(text.split("=")[0], text.split("=")[1]);

     }
 }
%>

因此，每当用户登录时，它都会从我的属性文件中获取值，但我想要的是通过 web.xml 加载我的属性文件，因此每当项目加载或服务器启动时，它都会从该属性文件加载连接仅一次，而不是每次用户登录时都会调用属性文件。

这是我的 Java 连接类，我在其中分配属性文件中的值:

ServletContext servletContext = getServletContext();
        String driverDB = servletContext.getAttribute("driver").toString();
        String conn_urlDB = servletContext.getAttribute("conn_url").toString();
        String userNameDB = servletContext.getAttribute("userName").toString();
        String passwordDB = servletContext.getAttribute("password").toString();
DBConnection.getDataBaseProperty(driverDB, conn_urlDB, userNameDB, passwordDB);

下面的 web.xml

    <?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>TouchPoint</display-name>

  <welcome-file-list>
    <welcome-file>Login.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <display-name>LoginServlet</display-name>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>com.touchpoint.controller.LoginServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/LoginServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <servlet-name>LogoutServlet</servlet-name>
    <servlet-class>com.touchpoint.controller.LogoutServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LogoutServlet</servlet-name>
    <url-pattern>/LogoutServlet</url-pattern>
  </servlet-mapping>
</web-app>

Answer 1

ServletContextListener 就是你的答案，

您可以查看这篇博文以更好地理解 https://www.journaldev.com/1945/servletcontextlistener-servlet-listener-example

将配置字符串放入 web.xml 文件中，然后通过 servletContextListener 在服务器启动时收到通知

以下是该博客文章的摘录:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>ServletListenerExample</display-name>

  <context-param>
    <param-name>DBUSER</param-name>
    <param-value>pankaj</param-value>
  </context-param>
  <context-param>
    <param-name>DBPWD</param-name>
    <param-value>password</param-value>
  </context-param>
  <context-param>
    <param-name>DBURL</param-name>
    <param-value>jdbc:mysql://localhost/mysql_db</param-value>
  </context-param>

  <listener>
    <listener-class>com.journaldev.listener.AppContextListener</listener-class>
  </listener>

您需要创建一个新类来监听服务器启动事件:

public class AppContextListener implements ServletContextListener {

    public void contextInitialized(ServletContextEvent servletContextEvent) {
        ServletContext ctx = servletContextEvent.getServletContext();

        String url = ctx.getInitParameter("DBURL");
        String u = ctx.getInitParameter("DBUSER");
        String p = ctx.getInitParameter("DBPWD");
}}