如何解决这个java.lang.ClassCastException：org.apache.tomcat.dbcp.dbcp.BasicDataSource无法强制转换为org.apache.tomcat.jdbc.pool.DataSource？

Question

我正在尝试使用池化在tomcat中进行数据库连接，这就是我的上下文：

<Resource name="jdbc/slingemp" auth="Container" type="javax.sql.DataSource"
               maxActive="100" maxIdle="30" maxWait="10000"
               username="root" password="root" driverClassName="com.mysql.jdbc.Driver"
               url="jdbc:mysql://localhost:3306/slingemp"/>

这就是我的web.xml：

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

这就是我与数据库连接的方式：

 package org.slingemp.jnditest;

import java.io.IOException;
import java.sql.Connection;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.tomcat.jdbc.pool.DataSource;

/**
 * Servlet implementation class JNDILookUpServlet
 */
@WebServlet("/JNDILookUpServlet")
public class JNDILookUpServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public JNDILookUpServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        try {
            Context initContext = new InitialContext();
            Context envContext  = (Context)initContext.lookup("java:/comp/env");
            DataSource ds = (DataSource)envContext.lookup("jdbc/slingemp");
            Connection conn = ds.getConnection();
            if(conn != null)System.out.println("Connected..");
            else System.out.println("Not connected...");
        } catch (Exception e) {
            e.printStackTrace();
        }
        response.sendRedirect("index.jsp");
    }


}

但它给了我以下例外：

java.lang.ClassCastException: org.apache.tomcat.dbcp.dbcp.BasicDataSource cannot be cast to org.apache.tomcat.jdbc.pool.DataSource

请帮我解决这个问题，

此致

Answer 1

您只是使用错误的导入。

替换这个：

import org.apache.tomcat.jdbc.pool.DataSource;

用这个：

import javax.sql.DataSource;

javax.sql.DataSource是所有DataSource实现必须继承的基接口。通常不建议针对此接口以外的任何其他方式进行开发。

Answer 2

如果遇到此错误，如何解决此 java.lang.ClassCastException ：

org.apache.tomcat.dbcp.dbcp.BasicDataSource无法转换为 org.apache.tomcat.jdbc.pool.DataSource

尝试替换：

import org.apache.tomcat.jdbc.pool.DataSource;

具有：

import javax.sql.DataSource;