Tomcat源码分析之—组件启动实现分析

Tomcat由多个组件组成，那么Tomcat是怎么对他们的生命周期进行管理的么，这里将从Tomcat源码去分析其生命周期的实现；

Bootstrape类为Tomcat的入口，所有的组件够通过实现Lifecycle接口来管理生命周期，Tomcat启动的时候只需调用Server容器的start()，然后父容器依序启动他所包含的子容器，关闭也是如此。

通过阅读源码可知一个Server里包含一个或多个Service，一个Service里包含一个Container，一个或多个Connector、Container又包含了Engine、Host、Context、Wrapper四个容器；

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Tomcat的组件启动顺序为：

StandardServer.start()——》StandardServer.startInternal() ——》StandardService().start()——StandardService.startInternal() ——>》StandardEngine().start() ——》StandardEngine.startInternal()—》StandardEngine中启动其他组件，组件关闭也是如此；

现在我们通过Demo简单模拟Tomcat的启动

模拟Demo UML类图

模拟Demo时序图

主要代码段如下：

Catalina类：

package co.solinx.Pattern.Observer;

/**
 * Created by LX on 2014/11/26.
 */
public class Catalina {

    public static void main(String[] args) {

        //Tomcat为多个组件组成的server为最外围最大的一个
        StandardServer server = new StandardServer();        //为server添加监听器
        server.addLifecycleListener(new ContextConfig());
        //添加一个service
        StandardService service = new StandardService();
        server.AddService(service);       //为service添加监听器
        service.addLifecycleListener(new ContextConfig());
        //添加一个engine
        StandardEngine standardEngine = new StandardEngine();        //为engine添加监听器
        standardEngine.addLifecycleListener(new EngineConfig());
        StandardHost standardHost = new StandardHost("localhost");
//        StandardHost testHost = new StandardHost("test");
//        standardHost.addLifecycleListener(new EngineConfig());
        standardEngine.addChild("localhost", standardHost);
//        standardEngine.addChild("test", testHost);
        //往service添加engine容器
        service.setContainer(standardEngine);
        try {
            server.start();
        } catch (LifecycleException e) {
            e.printStackTrace();
        }
    }

}

StandardServer类

package co.solinx.Pattern.Observer;

/**
 * Created by LX on 2014/11/26.
 */
public class StandardServer extends LifecycleBase implements Context {
    Service services[] = new Service[0];
    @Override
    protected void startInternal() throws LifecycleException {

        for (int i = 0; i < services.length; i++) {
            services[i].start();
        }

        System.out.println("StandardServer start");
    }
    public void AddService(Service service) {
        Service result[] = new Service[services.length + 1];
        System.arraycopy(services, 0, result, 0, services.length);
        result[services.length] = service;
        services = result;
    }
}

StandardService类：

package co.solinx.Pattern.Observer;

/**
 * Created by LX on 2014/11/26.
 */
public class StandardService extends LifecycleBase implements Service, Context {

    protected ContainerBase container = null;

    @Override
    protected void startInternal() throws LifecycleException {

        container.start();
        System.out.println("StandardService start");
    }

    public void setContainer(ContainerBase container) {
        this.container = container;
    }

}

StandardEngine类：

package co.solinx.Pattern.Observer;

/**
 * Created by LX on 2014/11/26.
 */
public class StandardEngine extends ContainerBase {
    @Override
    protected void startInternal() throws LifecycleException {
        super.startInternal();
        System.out.println("StandardEngine start");
    }

    protected void addChild(String key, Container container) {
        super.addChild(key, container);
    }
}

LifecycleSupport类：

package co.solinx.Pattern.Observer;

/**
 * Created by LX on 2014/11/26.
 * 代理了具体监听者
 */
public class LifecycleSupport {
    public LifecycleSupport(Lifecycle lifecycle) {
        super();
        this.lifecycle = lifecycle;
    }
    private Lifecycle lifecycle = null;
    private LifecycleListener listeners[] = new LifecycleListener[0];
    private final Object listenersLock = new Object(); // Lock object for changes to listeners
    public void addLifecycleListener(LifecycleListener listener) {
        synchronized (listenersLock) {
            LifecycleListener results[] =
                    new LifecycleListener[listeners.length + 1];
            for (int i = 0; i < listeners.length; i++)
                results[i] = listeners[i];
            results[listeners.length] = listener;
            listeners = results;
        }
    }
    public LifecycleListener[] findLifecycleListeners() {
        return listeners;
    }
    public void fireLifecycleEvent(String type, Object data) {
        LifecycleEvent event = new LifecycleEvent(lifecycle, type, data);
        LifecycleListener interested[] = listeners;
        for (int i = 0; i < interested.length; i++)
            interested[i].lifecycleEvent(event);
    }
    public void removeLifecycleListener(LifecycleListener listener) {
        synchronized (listenersLock) {
            int n = -1;
            for (int i = 0; i < listeners.length; i++) {
                if (listeners[i] == listener) {
                    n = i;
                    break;
                }
            }
            if (n < 0)
                return;
            LifecycleListener results[] =
                    new LifecycleListener[listeners.length - 1];
            int j = 0;
            for (int i = 0; i < listeners.length; i++) {
                if (i != n)
                    results[j++] = listeners[i];
            }
            listeners = results;
        }
    }
}

模拟程序运行结果：

文章首发地址：Solinx

http://www.solinx.co/archives/86