在把tomat JNDI數據源注入7

Question

我用一個項目工作@Resource註解訪問到Tomcat 7這裏，JNDI數據源是我的META-INF/context.xml的文件：

<?xml version="1.0" encoding="UTF-8"?> 
    <Context> 

    <Resource name="jdbc/ambes" auth="Container" type="javax.sql.DataSource" 
      maxActive="50" maxIdle="30" maxWait="10000" 
      username="root" password="" 
      driverClassName="com.mysql.jdbc.Driver" 
      url="jdbc:mysql://localhost:3306/ANTTestDb"/> 

    </Context> 

這是我的DAO類，數據源是通過成功的背景下查找服務注入到我的課，你看下面：

public class CoffeeDataBase { 

    private DataSource dataSource; 

    public CoffeeDataBase() { 

    try { 

     Context ctx = new InitialContext(); 
     dataSource = (DataSource) ctx.lookup("java:comp/env/jdbc/ambes"); 

     } catch (Exception e) { 
     e.printStackTrace(); 
    } 

    // other methods definition 

} 

，但是當我更換@Resourse anotaion這樣的查找服務：

@Resource(lookup="java:comp/env/jdbc/ambes") 
    public class CoffeeDataBase { 

    private DataSource dataSource; 

    public CoffeeDataBase() { 
    } 

    // other methods definition 

} 

我得到這個NullPointerExeption這樣的：

java.lang.NullPointerException 
    at com.ambestephen.dao.CoffeeDataBase.getCoffeeList(CoffeeDataBase.java:63) 
    at com.ambestephen.controller.ShowCoffees.doGet(ShowCoffees.java:16) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) 
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100) 
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) 
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041) 
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603) 
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) 
    at java.lang.Thread.run(Unknown Source) 

我也曾嘗試@Resource(name="jdbc/ambes")但同樣的異常！

Answer 1

Tomcat不支持@Resource注入。因此，您只能在Tomcat中使用上下文查找服務。你也可以使用依賴注入框架spring來注入dataSource，使你可以使用@Resource的註解。