我需要在我的Java ee应用程序中简化jdbc连接。我想在Spring中重写。它创建了太多的静态连接

Question

我有1个MySQL URL和4个数据库（方案），它们具有相同的表名，但行数不同（我的意思是要合并它们并不容易）。在我的Java应用程序中，我有一种方法可以根据某些（我自己的）条件选择数据库连接。比在参数中创建带有选定url的对象。但是我认为这是不正确的。

例如

jdbc:mysql://123.456.789.10:3306/First_Database
jdbc:mysql://123.456.789.10:3306/Second_Database
jdbc:mysql://123.456.789.10:3306/Third_Database
jdbc:mysql://123.456.789.10:3306/Fourth_Database

连接示例

public static void createConnectionFirst() throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.cj.jdbc.Driver");
        connect_1 = DriverManager.getConnection(url,user, password);
    }// and then same methods for connect_2 connect_3 and connect_4

当我在本地关闭时，出现异常：

14-Nov-2019 17:25:34.774 INFO [main] org.apache.catalina.core.StandardServer.await A valid shutdown command was received via the shutdown port. Stopping the Server instance.
14-Nov-2019 17:25:34.774 INFO [main] org.apache.coyote.AbstractProtocol.pause Pausing ProtocolHandler ["http-nio-8088"]
14-Nov-2019 17:25:34.879 INFO [main] org.apache.coyote.AbstractProtocol.pause Pausing ProtocolHandler ["ajp-nio-8009"]
14-Nov-2019 17:25:34.960 INFO [main] org.apache.catalina.core.StandardService.stopInternal Stopping service [Catalina]
14-Nov-2019 17:25:34.976 WARNING [main] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [sc] appears to have started a thread named [Abandoned connection cleanup thread] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.lang.System.currentTimeMillis(Native Method)
 org.apache.catalina.webresources.CachedResource.validateResource(CachedResource.java:82)
 org.apache.catalina.webresources.Cache.getResource(Cache.java:87)
 org.apache.catalina.webresources.StandardRoot.getResource(StandardRoot.java:216)
 org.apache.catalina.webresources.StandardRoot.getClassLoaderResource(StandardRoot.java:225)
 org.apache.catalina.loader.WebappClassLoaderBase.findResource(WebappClassLenter code hereoaderBase.java:936)
 org.apache.catalina.loader.WebappClassLoaderBase.getResource(WebappClassLoaderBase.java:1055)
 com.mysql.cj.jdbc.AbandonedConnectionCleanupThread.checkContextClassLoaders(AbandonedConnectionCleanupThread.java:96)
 com.mysql.cj.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:69)
 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
 java.lang.Thread.run(Thread.java:748)
14-Nov-2019 17:25:34.976 INFO [main] org.apache.coyote.AbstractProtocol.stop Stopping ProtocolHandler ["http-nio-8088"]
14-Nov-2019 17:25:34.976 INFO [main] org.apache.coyote.AbstractProtocol.stop Stopping ProtocolHandler ["ajp-nio-8009"]
14-Nov-2019 17:25:34.976 INFO [main] org.apache.coyote.AbstractProtocol.destroy Destroying ProtocolHandler ["http-nio-8088"]
14-Nov-2019 17:25:34.976 INFO [main] org.apache.coyote.AbstractProtocol.destroy Destroying ProtocolHandler ["ajp-nio-8009"]
Disconnected from server

Answer 1

[每当您使用Tomcat时，都可以使用以下命令（例如tomcat手册中的示例）在context.xml文件中预先配置所有数据源：

  <Resource name="jdbc/TestDB" auth="Container" type="javax.sql.DataSource"
           maxTotal="100" maxIdle="30" maxWaitMillis="10000"
           username="javauser" password="javadude" driverClassName="com.mysql.jdbc.Driver"
           url="jdbc:mysql://localhost:3306/javatest"/>

由于Tomcat负责管理连接，并且它决定根据需要打开或关闭它。

在您的代码中，您只是搜索具有特定名称的数据源并使用它。参见tomcat manual on how to configure datasources