java - 在 Spring 环境中泄漏 Tomcat JDBC MySQL 驱动程序

Question

目前我正在编写一个基于 Spring 和 JDBC 的 Web 应用程序，它与 Windows Server 2012 x64 上的 MySQL 数据库进行交互。 MySQL 数据库驱动程序是由 Tomcat 注册的，而不是由 servlet 本身注册的(正如很多人所做的那样)。

虽然我关闭了所有连接/准备好的语句/结果集，但 Tomcat 在重新启动期间记录了可能的内存泄漏，我不知道为什么。此外，几天后服务器崩溃(读取:超时)，可能是因为泄漏。

$APACHE_DIR/conf/context.xml:

<?xml version='1.0' encoding='utf-8'?>
<Context>
    <WatchedResource>WEB-INF/web.xml</WatchedResource>
    <WatchedResource>${catalina.base}/conf/web.xml</WatchedResource>
    <Resource name="jdbc/testservlet" 
              global="jdbc/testservlet"
              type="javax.sql.DataSource"              
              username="root"
              password="123456aA"
              driverClassName="com.mysql.jdbc.Driver"
              url="jdbc:mysql://localhost:3306/testservlet"
              maxTotal="10"
              maxIdle="10"
              maxWaitMillis="10000"
              removeAbandonedTimeout="300"            
              defaultAutoCommit="true" />
</Context>

$APACHE_DIR/webapps/testservlet/META-INF/context.xml:

<?xml version='1.0' encoding='utf-8'?>
<Context>
    <ResourceLink name="jdbc/testservlet" global="jdbc/testservlet" type="javax.sql.DataSource" />
</Context>

$PROJECT_DIR/DatabaseConfiguration.java

package com.example.testservlet.configuration;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.sql.DataSource;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class DatabaseConfiguration
{
    @Bean
    public DataSource getDataSource() throws Exception
    {
        Context initialContext = new InitialContext();
        Context environmentContext = (Context) initialContext.lookup("java:comp/env");
        DataSource dataSource = (DataSource) environmentContext.lookup("jdbc/testservlet");
        return dataSource;
    }
}

$PROJECT_DIR/HomeController.java

package com.example.testservlet.controller;

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.ResultSet;

import javax.sql.DataSource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class HomeController
{
    @Autowired
    DataSource datasource;

    @ResponseBody
    @RequestMapping(value = "/", method = RequestMethod.GET)
    public void home() throws Exception
    {
        Connection connection = null;
        ResultSet resultset = null;
        try
        {
            connection = datasource.getConnection();
            DatabaseMetaData metadata = connection.getMetaData();
            resultset = metadata.getTables(null, null, "%", null);
            while(resultset.next())
            {
              System.out.println("Table: " + resultset.getString(3));
            }
        }
        finally
        {
            System.out.println("Final block start");
            try{ connection.close(); } catch(Exception exception) { throw new Exception("Database error"); }
            try{ resultset.close(); } catch(Exception exception) { throw new Exception("Database error"); }
            System.out.println("Final block end");
        }
    }
}

$PROJECT_ROOT/pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>testservlet</artifactId>
    <packaging>war</packaging>
    <version>0.1.0-SNAPSHOT</version>
    <name>testservlet</name>
    <dependencies>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>4.1.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>4.1.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>4.1.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>4.1.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.38</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <build>
        <finalName>testservlet</finalName>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
            </resource>
        </resources>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                    <archive>
                        <manifest>
                            <addClasspath>true</addClasspath>
                            <classpathPrefix>lib/</classpathPrefix>
                        </manifest>
                    </archive>
                    <webResources>
                        <resource>
                            <directory>${project.basedir}/src/main/resources
                            </directory>
                        </resource>
                    </webResources>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

MySQL 驱动程序作为“mysql-connector-java.jar”(版本 5.1.38)安装在 Tomcat lib 目录中，数据库配置由 Spring 框架调用。对 localhost:8080/testservlet 的 HTTP 请求 + Tomcat 重新启动导致以下日志:

25-Jan-2016 19:11:28.006 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Server version:        Apache Tomcat/8.0.30
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Server built:          Dec 1 2015 22:30:46 UTC
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Server number:         8.0.30.0
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log OS Name:               Windows Server 2012 R2
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log OS Version:            6.3
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Architecture:          amd64
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Java Home:             C:\Program Files\Java\jdk1.8.0_66\jre
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log JVM Version:           1.8.0_66-b18
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log JVM Vendor:            Oracle Corporation
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log CATALINA_BASE:         C:\Users\simonwaechter\Downloads\apache-tomcat-8.0.30-windows-x64
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log CATALINA_HOME:         C:\Users\simonwaechter\Downloads\apache-tomcat-8.0.30-windows-x64
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Djava.util.logging.config.file=C:\Users\simonwaechter\Downloads\apache-tomcat-8.0.30-windows-x64\conf\logging.properties
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Djava.endorsed.dirs=C:\Users\simonwaechter\Downloads\apache-tomcat-8.0.30-windows-x64\endorsed
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Dcatalina.base=C:\Users\simonwaechter\Downloads\apache-tomcat-8.0.30-windows-x64
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Dcatalina.home=C:\Users\simonwaechter\Downloads\apache-tomcat-8.0.30-windows-x64
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Djava.io.tmpdir=C:\Users\simonwaechter\Downloads\apache-tomcat-8.0.30-windows-x64\temp
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.core.AprLifecycleListener.lifecycleEvent Loaded APR based Apache Tomcat Native library 1.1.33 using APR version 1.5.1.
25-Jan-2016 19:11:28.037 INFO [main] org.apache.catalina.core.AprLifecycleListener.lifecycleEvent APR capabilities: IPv6 [true], sendfile [true], accept filters [false], random [true].
25-Jan-2016 19:11:28.617 INFO [main] org.apache.catalina.core.AprLifecycleListener.initializeSSL OpenSSL successfully initialized (OpenSSL 1.0.1m 19 Mar 2015)
25-Jan-2016 19:11:28.866 INFO [main] org.apache.coyote.AbstractProtocol.init Initializing ProtocolHandler ["http-apr-8080"]
25-Jan-2016 19:11:28.881 INFO [main] org.apache.coyote.AbstractProtocol.init Initializing ProtocolHandler ["ajp-apr-8009"]
25-Jan-2016 19:11:28.881 INFO [main] org.apache.catalina.startup.Catalina.load Initialization processed in 1407 ms
25-Jan-2016 19:11:28.929 INFO [main] org.apache.catalina.core.StandardService.startInternal Starting service Catalina
25-Jan-2016 19:11:28.929 INFO [main] org.apache.catalina.core.StandardEngine.startInternal Starting Servlet Engine: Apache Tomcat/8.0.30
25-Jan-2016 19:11:29.006 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployWAR Deploying web application archive C:\Users\simonwaechter\Downloads\apache-tomcat-8.0.30-windows-x64\webapps\testservlet.war
25-Jan-2016 19:11:30.901 INFO [localhost-startStop-1] org.apache.tomcat.dbcp.dbcp2.BasicDataSourceFactory.getObjectInstance Name = testservlet Ignoring unknown property: value of "JCG Example MySQL database." for "description" property
25-Jan-2016 19:11:30.901 INFO [localhost-startStop-1] org.apache.tomcat.dbcp.dbcp2.BasicDataSourceFactory.getObjectInstance Name = testservlet Ignoring unknown property: value of "jdbc/testservlet" for "global" property
25-Jan-2016 19:11:31.010 INFO [localhost-startStop-1] org.apache.jasper.servlet.TldScanner.scanJars At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.
25-Jan-2016 19:11:31.213 INFO [localhost-startStop-1] org.springframework.web.context.ContextLoader.initWebApplicationContext Root WebApplicationContext: initialization started
25-Jan-2016 19:11:31.213 INFO [localhost-startStop-1] org.springframework.web.context.support.AnnotationConfigWebApplicationContext.prepareRefresh Refreshing Root WebApplicationContext: startup date [Mon Jan 25 19:11:31 CET 2016]; root of context hierarchy
25-Jan-2016 19:11:31.369 INFO [localhost-startStop-1] org.springframework.web.context.support.AnnotationConfigWebApplicationContext.loadBeanDefinitions Found 2 annotated classes in package [com.example.testservlet.configuration]
25-Jan-2016 19:11:32.141 INFO [localhost-startStop-1] org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping.registerHandlerMethod Mapped "{[/],methods=[GET],params=[],headers=[],consumes=[],produces=[],custom=[]}" onto public void com.example.testservlet.controller.HomeController.home() throws java.lang.Exception
25-Jan-2016 19:11:32.187 INFO [localhost-startStop-1] org.springframework.web.servlet.handler.SimpleUrlHandlerMapping.registerHandler Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.DefaultServletHttpRequestHandler]
25-Jan-2016 19:11:32.437 INFO [localhost-startStop-1] org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.initControllerAdviceCache Looking for @ControllerAdvice: Root WebApplicationContext: startup date [Mon Jan 25 19:11:31 CET 2016]; root of context hierarchy
25-Jan-2016 19:11:32.671 INFO [localhost-startStop-1] org.springframework.web.context.ContextLoader.initWebApplicationContext Root WebApplicationContext: initialization completed in 1458 ms
25-Jan-2016 19:11:32.749 INFO [localhost-startStop-1] org.springframework.web.servlet.DispatcherServlet.initServletBean FrameworkServlet 'DispatcherServlet': initialization started
25-Jan-2016 19:11:32.781 INFO [localhost-startStop-1] org.springframework.web.servlet.DispatcherServlet.initServletBean FrameworkServlet 'DispatcherServlet': initialization completed in 32 ms
25-Jan-2016 19:11:32.829 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployWAR Deployment of web application archive C:\Users\simonwaechter\Downloads\apache-tomcat-8.0.30-windows-x64\webapps\testservlet.war has finished in 3,807 ms
25-Jan-2016 19:11:32.829 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["http-apr-8080"]
25-Jan-2016 19:11:32.843 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["ajp-apr-8009"]
25-Jan-2016 19:11:32.843 INFO [main] org.apache.catalina.startup.Catalina.start Server startup in 3959 ms
25-Jan-2016 19:11:45.074 INFO [main] org.apache.catalina.core.StandardServer.await A valid shutdown command was received via the shutdown port. Stopping the Server instance.
25-Jan-2016 19:11:45.074 INFO [main] org.apache.coyote.AbstractProtocol.pause Pausing ProtocolHandler ["http-apr-8080"]
25-Jan-2016 19:11:45.137 INFO [main] org.apache.coyote.AbstractProtocol.pause Pausing ProtocolHandler ["ajp-apr-8009"]
25-Jan-2016 19:11:45.199 INFO [main] org.apache.catalina.core.StandardService.stopInternal Stopping service Catalina
25-Jan-2016 19:11:45.199 INFO [localhost-startStop-2] org.springframework.web.context.support.AnnotationConfigWebApplicationContext.doClose Closing Root WebApplicationContext: startup date [Mon Jan 25 19:11:31 CET 2016]; root of context hierarchy
25-Jan-2016 19:11:45.199 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [testservlet] 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.Object.wait(Native Method)
 java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
 com.mysql.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:43)
25-Jan-2016 19:11:45.215 INFO [main] org.apache.coyote.AbstractProtocol.stop Stopping ProtocolHandler ["http-apr-8080"]
25-Jan-2016 19:11:45.309 INFO [main] org.apache.coyote.AbstractProtocol.stop Stopping ProtocolHandler ["ajp-apr-8009"]
25-Jan-2016 19:11:45.371 INFO [main] org.apache.coyote.AbstractProtocol.destroy Destroying ProtocolHandler ["http-apr-8080"]
25-Jan-2016 19:11:45.371 INFO [main] org.apache.coyote.AbstractProtocol.destroy Destroying ProtocolHandler ["ajp-apr-8009"]

我不知道为什么会发生这种泄漏。有很多答案，例如注销 JDBC 驱动程序，但很少有人在共享/托管 Tomcat 环境中处理驱动程序，在这种环境中，其他 servlet 可能会访问相同的 JDBC 驱动程序。

Answer 1

我们最终得到了 Guillaume 的回答并使用了监听器。

我仍然不知道是什么导致了零星的崩溃，但是 Oracle MySQL 服务器的更新解决了这个问题。