How to unload child Spring context?

Question

ContextLoaderListener initializes and closes the root web application context.

What mechanism, if any, is required to close the child WebApplicationContext created by the DispatcherServlet?

web.xml:

    <context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>                      
      /WEB-INF/applicationContext.xml
    </param-value>
</context-param>
<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet>
    <servlet-name>myservlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/myservlet-servlet.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

I'm seeing classes hanging around after stopping applications in Tomcat, wonder if this would help?

Edit: I was never able to find the classes, please see my question for details: no-gc-root-found

Thank you.

The Application Details (in hope of getting a clue to solve permgen) Spring 3.2.1 Spring security 3.1.3 Hibernate 4.1.9 Tomcat 7.42

The application's internal name is 'derby', not to be confused with the DB.

pom.xml

    <dependencies>
    <dependency>
        <groupId>javax.inject</groupId>
        <artifactId>javax.inject</artifactId>
        <version>1</version>
        <!-- <scope>provided</scope> -->
    </dependency>

    <dependency>
        <groupId>javax.mail</groupId>
        <artifactId>mail</artifactId>
        <version>1.4.5</version>
        <exclusions>
            <exclusion>
                <groupId>javax.activation</groupId>
                <artifactId>activation</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi</artifactId>
        <version>3.0.2-FINAL</version>
    </dependency>

    <dependency>
        <groupId>commons-io</groupId>
        <artifactId>commons-io</artifactId>
        <version>2.4</version>
    </dependency>

    <dependency>
        <groupId>commons-fileupload</groupId>
        <artifactId>commons-fileupload</artifactId>
        <version>1.2.2</version>
    </dependency>

    <dependency>
        <groupId>commons-lang</groupId>
        <artifactId>commons-lang</artifactId>
        <version>2.6</version>
    </dependency>

    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>${hibernate.version}</version>
    </dependency>

    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>${hibernate.version}</version>
    </dependency>

    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-validator</artifactId>
        <version>4.3.1.Final</version>
    </dependency>

    <dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-digester3</artifactId>
        <version>3.2</version>
        <classifier>with-deps</classifier>
    </dependency>
    <dependency>
        <groupId>commons-beanutils</groupId>
        <artifactId>commons-beanutils</artifactId>
        <version>1.8.3</version>
    </dependency>

    <dependency>
        <groupId>org.apache.tiles</groupId>
        <artifactId>tiles-extras</artifactId>
        <version>${org.apache.tiles.version}</version>
        <exclusions>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-nop</artifactId>
            </exclusion>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-api</artifactId>
            </exclusion>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>jcl-over-slf4j</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

    <dependency>
        <groupId>org.apache.tiles</groupId>
        <artifactId>tiles-core</artifactId>
        <version>${org.apache.tiles.version}</version>
        <exclusions>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-nop</artifactId>
            </exclusion>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-api</artifactId>
            </exclusion>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>jcl-over-slf4j</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.apache.tiles</groupId>
        <artifactId>tiles-api</artifactId>
        <version>${org.apache.tiles.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tiles</groupId>
        <artifactId>tiles-jsp</artifactId>
        <version>${org.apache.tiles.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tiles</groupId>
        <artifactId>tiles-servlet</artifactId>
        <version>${org.apache.tiles.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tiles</groupId>
        <artifactId>tiles-template</artifactId>
        <version>${org.apache.tiles.version}</version>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.17</version>
    </dependency>

    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>1.7.2</version>
    </dependency>

    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-ext</artifactId>
        <version>1.7.2</version>
    </dependency>

    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
        <version>1.7.2</version>
    </dependency>

    <dependency>
        <groupId>net.sf.dozer</groupId>
        <artifactId>dozer</artifactId>
        <version>5.4.0</version>
        <exclusions>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>jcl-over-slf4j</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-mapper-asl</artifactId>
        <version>1.9.11</version>
    </dependency>

    <dependency>
        <groupId>org.testng</groupId>
        <artifactId>testng</artifactId>
        <version>6.8</version>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.easymock</groupId>
        <artifactId>easymock</artifactId>
        <version>3.1</version>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.dbunit</groupId>
        <artifactId>dbunit</artifactId>
        <version>2.4.9</version>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>servlet-api</artifactId>
        <version>2.5</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>javax.servlet.jsp</groupId>
        <artifactId>jsp-api</artifactId>
        <version>2.2</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>taglibs</groupId>
        <artifactId>standard</artifactId>
        <version>1.1.2</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework.integration</groupId>
        <artifactId>spring-integration-mail</artifactId>
        <version>2.2.1.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>${org.springframework.version}</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-orm</artifactId>
        <version>${org.springframework.version}</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-web</artifactId>
        <version>${org.springframework.version}</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>${org.springframework.version}</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-test</artifactId>
        <version>${org.springframework.version}</version>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-core</artifactId>
        <version>${org.springframework.security.version}</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-web</artifactId>
        <version>${org.springframework.security.version}</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-config</artifactId>
        <version>${org.springframework.security.version}</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-acl</artifactId>
        <version>${org.springframework.security.version}</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-taglibs</artifactId>
        <version>${org.springframework.security.version}</version>
    </dependency>
</dependencies>

I used to create DB Connection Pool within Spring, have moved it to META-INF/context.xml hoping to get rid of any lingering Thread created by the Pool.

catalina.out after shutdown.bat is run

Sep 12, 2013 12:44:15 PM org.apache.catalina.core.AprLifecycleListener init
INFO: Loaded APR based Apache Tomcat Native library 1.1.27 using APR version 1.4.6.
Sep 12, 2013 12:44:15 PM org.apache.catalina.core.AprLifecycleListener init
INFO: APR capabilities: IPv6 [true], sendfile [true], accept filters [false], random  [true].
Sep 12, 2013 12:44:15 PM org.apache.catalina.core.AprLifecycleListener initializeSSL
INFO: OpenSSL successfully initialized (OpenSSL 1.0.1d 5 Feb 2013)
Sep 12, 2013 12:44:16 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-apr-8188"]
Sep 12, 2013 12:44:16 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["ajp-apr-8009"]
Sep 12, 2013 12:44:16 PM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 1441 ms
Sep 12, 2013 12:44:16 PM org.apache.catalina.core.StandardService startInternal
INFO: Starting service Catalina
Sep 12, 2013 12:44:16 PM org.apache.catalina.core.StandardEngine startInternal
INFO: Starting Servlet Engine: Apache Tomcat/7.0.42
Sep 12, 2013 12:44:16 PM org.apache.catalina.startup.HostConfig deployWAR
INFO: Deploying web application archive J:\Java\Tomcat\apache-tomcat-7.0.42\webapps\derby.war
Sep 12, 2013 12:44:28 PM org.apache.catalina.startup.HostConfig deployDirectory
INFO: Deploying web application directory J:\Java\Tomcat\apache-tomcat-7.0.42\webapps\manager
Sep 12, 2013 12:44:28 PM org.apache.catalina.startup.HostConfig deployDirectory
INFO: Deploying web application directory J:\Java\Tomcat\apache-tomcat-7.0.42\webapps\ROOT
Sep 12, 2013 12:44:28 PM org.apache.coyote.AbstractProtocol start
INFO: Starting ProtocolHandler ["http-apr-8188"]
Sep 12, 2013 12:44:28 PM org.apache.coyote.AbstractProtocol start
INFO: Starting ProtocolHandler ["ajp-apr-8009"]
Sep 12, 2013 12:44:28 PM org.apache.catalina.startup.Catalina start
INFO: Server startup in 12691 ms
Sep 12, 2013 12:45:14 PM org.apache.catalina.core.StandardServer await
INFO: A valid shutdown command was received via the shutdown port. Stopping the Server instance.
Sep 12, 2013 12:45:14 PM org.apache.coyote.AbstractProtocol pause
INFO: Pausing ProtocolHandler ["http-apr-8188"]
Sep 12, 2013 12:45:14 PM org.apache.coyote.AbstractProtocol pause
INFO: Pausing ProtocolHandler ["ajp-apr-8009"]
Sep 12, 2013 12:45:14 PM org.apache.catalina.core.StandardService stopInternal
INFO: Stopping service Catalina
Sep 12, 2013 12:45:15 PM org.apache.coyote.AbstractProtocol stop
INFO: Stopping ProtocolHandler ["http-apr-8188"]
Sep 12, 2013 12:45:15 PM org.apache.coyote.AbstractProtocol stop
INFO: Stopping ProtocolHandler ["ajp-apr-8009"]
Sep 12, 2013 12:45:15 PM org.apache.coyote.AbstractProtocol destroy
INFO: Destroying ProtocolHandler ["http-apr-8188"]
Sep 12, 2013 12:45:15 PM org.apache.coyote.AbstractProtocol destroy
INFO: Destroying ProtocolHandler ["ajp-apr-8009"]

Tomcat Manager shows this message after 'Find leaks' is clicked. enter image description here

@Sotirios Delimanolis please see my update, I was never able to hunt down the lingering classes. — kmansoor, Sep 11 '13 at 20:34
When you `shutdown.sh`, can you post what the `catalina.out` logs? — Sotirios Delimanolis, Sep 11 '13 at 20:36
You accepted the answer, but I don't know if it solves anything. You might want to consider putting the log. I've had issues like this before. — Sotirios Delimanolis, Sep 11 '13 at 21:04
Are you using commons-logging and/or cglib? Sometimes that leads to static references to classloaders, keeping everything (or a lot) in memory. — M. Deinum, Sep 12 '13 at 07:06
@Sotirios Delimanolis, I accepted your answer as it expressely answered the question. But no, my wider woes, permgen, is still unsolved. I have updated the question with pom and the log. If you could please take a look? Thanks. — kmansoor, Sep 12 '13 at 16:53
@M. Deinum, yes I do see them in the 'resolved dependencies' tab when viewing pom.xml in eclipse. — kmansoor, Sep 12 '13 at 16:54
Your application shutsdown gracefully from what I can see in the logs. I guess the leak is normal if you only stopped `derby`, but the others are still running. In other words, the class loader has loaded the class required by `derby`, but doesn't unload them after it stops it. I don't know that it even can... — Sotirios Delimanolis, Sep 12 '13 at 17:04
You are using SLF4J next to commons-logging. Start with excluding commons-logging and include the `jcl-over-slf4j` dependency from org.slf4j. That way you have only a single logging abstraction. http://stackoverflow.com/questions/5635255/permgen-out-of-memory-reasons might be related. — M. Deinum, Sep 13 '13 at 06:11
Removed commons-logging, but classes still linger around. Thanks for the suggestion though. — kmansoor, Sep 13 '13 at 18:04

score 1 · Accepted Answer · answered Sep 11 '13 at 20:31

The DispatcherServlet (through FrameworkServlet) also closes its WebApplicationContext

@Override
public void destroy() {
    getServletContext().log("Destroying Spring FrameworkServlet '" + getServletName() + "'");
    if (this.webApplicationContext instanceof ConfigurableApplicationContext) {
        ((ConfigurableApplicationContext) this.webApplicationContext).close();
    }
}

The classes you are seeing are most likely Threads leftover from a connection pool or possibly an ExecutorService. There are dirty ways to force those to close as well.

How to unload child Spring context?

1 Answers1