我无法在 tomcat 中使用 JNDI 连接 MySQL

Question

I did everything in this : how to connect tomcat 7 and mysql
But it still isn't working..... why? What have I missed?

Enviroment

OS : Win7
Eclipse : J2EE Mars
Tomcat : tomcat 8.0
java : 1.8.0_73
db name : test
username: root
password: 123

---

controller:

writeDB testDB = new writeDB(tablename);

---

writeDB.java

....
Class.forName("com.mysql.jdbc.Driver"); 
try{
      Context initContext = new InitialContext();
      Context envContext = (Context)initContext.lookup("java:/comp/env");
      //-------error------- 
      dataSource = (DataSource) envContext.lookup("jdbc/test");
      //-------error-------
   }catch(NamingException ex)
   {
      throw new RuntimeException(ex);   
   }

---

web.xml (in my project)

<!-- MySQL JNDI -->
<resource-ref>
    <description>MySQL DB</description>
    <res-ref-name>jdbc/test</res-ref-name>
    <res-type>javax.sql.DataSource</res-type>
    <res-auth>Container</res-auth>
</resource-ref>

---

context.xml

(in TOMCAT_HOME/conf)
(Also in workspace\\Servers\\Tomcat v8.0 Server at localhost-config)

<?xml version="1.0" encoding="UTF-8"?>
<Context antiJARLocking="true" path="/eatST">
<Resource 
    name="jdbc/test"
    auth="Container" 
    type="javax.sql.DataSource"
    maxActice="100" 
    maxIdle="30" 
    maxWait="10000" 
    username="root"
    password="123" 
    driverClassName="com.mysql.jdbc.Driver"
    url="jdbc:mysql://localhost:3306/test?
         useUnicode=true&amp;characterEncoding=UTF8"
    factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
 />
 </Context>

---

Logs

Servlet.service() for servlet [commentCtr] in context 
with path [/eatST]      threw exception
java.lang.ClassCastException: org.apache.tomcat.dbcp.dbcp2.BasicDataSource   
cannot be cast to javax.activation.DataSource
     at com.joe.db.writeDB.<init>(writeDB.java:58)
     at com.joe.servlet.CommentCtr.doPost(CommentCtr.java:38)
     at ............

Answer 1

You've imported (and presumable programmed to) an incorrect DataSource . Your exception ( java.lang.ClassCastException ... cannot be cast to javax.activation.DataSource ) is telling you that you have used javax.activation.DataSource , but you wanted javax.sql.DataSource . Modify com.joe.db.writeDB and change

import javax.activation.DataSource;

to

import javax.sql.DataSource;

Also, you don't need Class.forName("com.mysql.jdbc.Driver"); (it doesn't hurt anything, but JDBC drivers register themselves now).