Tomcat源码笔记（四）StandardService_standardservice.connector.startfailed

上节看了容器的初始化和启动，知道了Tomcat初始化和启动都是由Server.init()，Server.start()，层层向下依次触发各个组件的initInternal()，startInternal()方法进行初始化和启动，从本片开始，就从各组件的初始化和启动开始读源码（本文Tomcat8.5）

本文的Service实现类是StandardService，内部从配置文件中看到，内部是多个Connector和一个Engine组成，来看代码

initInternal() / startInternal()

就是调用各子组件（Engine\Connector\Mapper\Executor）的初始化和启动方法

public class StandardService extends LifecycleMBeanBase implements Service {
    // 父组件Server的引用
    private Server server = null;
 
    // 多个Connector，每种连接一个Connector  http,https,向相同协议不同端口的连接等
    protected Connector connectors[] = new Connector[0];
    
    // 用来synchronized
    private final Object connectorsLock = new Object();
 
    // Service下 和Connector和Engine同级别的组件Executor，StandardThreadExecutor
    // ThreadPoolExecutor的封装
    protected final ArrayList<Executor> executors = new ArrayList<>();
 
    // 子组件Engine
    private Engine engine = null;
 
    protected final Mapper mapper = new Mapper();
 
    protected final MapperListener mapperListener = new MapperListener(this);
 
    @Override
    protected void initInternal() throws LifecycleException {
        // 注册当前对象MBean
        super.initInternal();
 
        // 初始化engine
        if (engine != null) {
            engine.init();
        }
 
        // 初始化Executor
        for (Executor executor : findExecutors()) {
            if (executor instanceof JmxEnabled) {
                ((JmxEnabled) executor).setDomain(getDomain());
            }
            executor.init();
        }
 
        // 初始化mapperListener，只是注册JMX
        mapperListener.init();
 
        // 初始化Connector
        synchronized (connectorsLock) {
            for (Connector connector : connectors) {
                try {
                    connector.init();
                } catch (Exception e) {
                    String message = sm.getString(
                            "standardService.connector.initFailed", connector);
                    log.error(message, e);
 
                    if (Boolean.getBoolean("org.apache.catalina.startup.EXIT_ON_INIT_FAILURE"))
                        throw new LifecycleException(message);
                }
            }
        }
    }
 
   protected void startInternal() throws LifecycleException {
 
        // 设置Starting状态
        setState(LifecycleState.STARTING);
 
        // 启动Engine
        if (engine != null) {
            synchronized (engine) {
                engine.start();
            }
        }
 
        // 启动executor
        synchronized (executors) {
            for (Executor executor: executors) {
                executor.start();
            }
        }
 
        //mapperListener启动
        mapperListener.start();
 
        // Connector启动
        synchronized (connectorsLock) {
            for (Connector connector: connectors) {
                try {
                    // If it has already failed, don't try and start it
                    if (connector.getState() != LifecycleState.FAILED) {
                        connector.start();
                    }
                } catch (Exception e) {
                    log.error(sm.getString(
                            "standardService.connector.startFailed",
                            connector), e);
                }
            }
        }
    }
}

Connector和Engine下节看

Mapper

对请求进行路由， Mapper中有MappedHost数组，Mapper内部类有MappedHost\MappedContext\MappedWrapper 几种，和Container容器有四个子接口Engine,Host,Context,Wrapper一一对应

目的是请求来时快速查找匹配的具体的wrapper(Servlet)

public final class Mapper {
   volatile MappedHost[] hosts = new MappedHost[0];
}

 

在tomcat服务器中，有多个service，每个service有一个engine，而一个engine可以部署多个host，一个host又可以部署多个context，一个context多个wrapper，Mapper类中也符合这个层次。

MapperListener

查询当前Engine所部署的相关应用更新到mapper中，并监听Engine下容器动态更新mapper

public class MapperListener extends LifecycleMBeanBase
        implements ContainerListener, LifecycleListener {
    private final Mapper mapper;
 
    private final Service service;
 
    public MapperListener(Service service) {
        this.service = service;
        this.mapper = service.getMapper();
    }
}

首先MapperListener继承 LifecycleMBeanBase，说明对象的启动会被注册到jmx上面去，其次实现了两个Listener，LifecycleListener之前见过，监听顶层的生命周期变更事件触发lifecycleEvent()方法，ContainerListener监听容器Container的变更事件触发containerEvent()方法

public interface ContainerListener {
    public void containerEvent(ContainerEvent event);
}

org.apache.catalina.mapper.MapperListener#startInternal

   @Override
    public void startInternal() throws LifecycleException {
        // 设置启动状态
        setState(LifecycleState.STARTING);
 
        Engine engine = service.getContainer();
        if (engine == null) {
            return;
        }
 
        //  <Engine name="Catalina" defaultHost="localhost">
        //  获取defaultHost属性， 并检查是否存在对应的<Host >标签
        findDefaultHost();
 
        // 将Engine及其子容器都注册这个MapperListener对象
        addListeners(engine);
 
        // 获取engine的所有Host配置，注册到Mapper中
        // 注册host又会把其下所有context注册，接着往下注册所有wrapper
        Container[] conHosts = engine.findChildren();
        for (Container conHost : conHosts) {
            Host host = (Host) conHost;
            if (!LifecycleState.NEW.equals(host.getState())) {
                // Registering the host will register the context and wrappers
                registerHost(host);
            }
        }
    }

  private void registerHost(Host host) {
 
        String[] aliases = host.findAliases();
 
        // mapper中增加host
        mapper.addHost(host.getName(), aliases, host);
 
        // 注册context到mapper
        for (Container container : host.findChildren()) {
            if (container.getState().isAvailable()) {
                registerContext((Context) container);
            }
        }
    }

org.apache.catalina.mapper.MapperListener#containerEvent

监听器回调方法，根据事件注册或移除监听器，更新mapper

 org.apache.catalina.mapper.MapperListener#lifecycleEvent

也是根据事件更新mapper