java - 启动连接池时数据源出现NullPointerException

Question

所以我在context.xml中有一个代码，其中包含数据库连接的信息

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

<Resources name="jdbc/murach" auth="Containter"
    driverClassName="com.mysql.jdbc.Driver"
    url="jdbc:mysql://localhost:3306/murach"
    username="root" password="root"
    maxActive="100" maxIdle="30" maxWait="10000"
    logAbandoned="true" removeAbandoned="true"
    removeAbandonedTimeout="60" type="javax.sql.DataSource" />

 <ResourceLink name="jdbc/murach"
         global="jdbc/mydb"
          type="javax.sql.DataSource" />

对于连接池，我创建了一个类来启动并将其连接到数据库。错误从 getConnection() 方法开始。请问我应该在查找中真正添加什么才能使其工作。顺便说一下，在datasource.getConnection()的返回中，错误是NullPointerException。

package lars.data;

import java.sql.Connection;
import java.sql.SQLException;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;


public class ConnectionPool {
    private static ConnectionPool pool = null;
    private static DataSource dataSource = null;

    private ConnectionPool() {
        try {
            InitialContext ic = new InitialContext();
            dataSource = (DataSource) ic.lookup("java:/comp/env/jdbc/murach");
            System.out.print(dataSource);
        } catch (NamingException e) {
            System.out.println(e);
        }
    }

    public static synchronized ConnectionPool getInstance() {
        if (pool == null) {
            pool = new ConnectionPool();
        }
        return pool;
    }

    public Connection getConnection() {
        try {
            return dataSource.getConnection();
        } catch (SQLException e) {
            System.out.println(e);
            return null;
        }
    }

    public void freeConnection(Connection c) {
        try {
            c.close();
        } catch (SQLException e) {
            System.out.println(e);
        }
    }
}

Answer 1

我相信您的问题在于 ResourceLink 的配置，尤其是属性 global 的值，该值应与 Resource< 中定义的值匹配，应该是:

 <ResourceLink name="jdbc/murach"
         global="jdbc/murach"
          type="javax.sql.DataSource" />

global: The name of the linked global resource in the global JNDI context.

name: The name of the resource link to be created, relative to the java:comp/env context.

注意事项1:定义资源的节点名称是Resource，而不是Resources。换句话说，它应该是:

<Resource name="jdbc/murach" ... />

NB 2:您应该尝试ic.lookup("java:comp/env/jdbc/murach")