Tomcat 總體架構(gòu)-源碼組織

開篇

?這篇文章主要是將Tomcat的架構(gòu)圖從源碼角度解析了一下庐完，基本上就是把圖和源碼串聯(lián)起來。

Tomcat 總體架構(gòu)

Catalina - 入口

? Catalina對象包含Server對象變量熔萧，在初始化過程中通過Digester注入Server來實現(xiàn)。

protected Server server = null

public class Catalina {

    protected boolean await = false;

    protected String configFile = "conf/server.xml";

    protected ClassLoader parentClassLoader = Catalina.class.getClassLoader();

    // Catalina包含StandardServer對象
    protected Server server = null;

    protected boolean useShutdownHook = true;

    protected Thread shutdownHook = null;

    protected boolean useNaming = true;

    protected boolean loaded = false;
}

Server - StandardServer

? StandardServer實現(xiàn)了Server接口和Lifecycle接口僚祷，核心變量如下：

port字段存儲<server>標簽的port屬性
shutdown字段存儲<server>標簽的shutdown屬性
Service services[]存儲Server標簽子標簽的<Service>標簽對象
private Service services[] = new Service[0]

public final class StandardServer extends LifecycleMBeanBase implements Server {

    public StandardServer() {

        super();
        // 省略相關(guān)代碼
    }

    // 省略相關(guān)代碼

    // 對比server.xml中<server>標簽的內(nèi)容的port
    private int port = 8005;

    // 維護Service的對象佛致，
    private Service services[] = new Service[0];

    private final Object servicesLock = new Object();
    
    // 對比server.xml中<server>標簽的內(nèi)容的shutdown
    private String shutdown = "SHUTDOWN";

    // 省略相關(guān)代碼
}

Service - StandardService

? StandardService實現(xiàn)了Server接口和Lifecycle接口，核心變量如下：

Connector connectors[] 變量保存監(jiān)聽的Connector對象辙谜。
ArrayList<Executor> executors 變量保存多線程對象Executor對象俺榆。
Engine engine變量保存Service標簽內(nèi)部的Engine對象。
Mapper mapper變量保存Mapper對象装哆。
MapperListener mapperListener變量保存MapperListener對象罐脊。

public class StandardService extends LifecycleMBeanBase implements Service {
    private String name = null;

    private Server server = null;

    protected final PropertyChangeSupport support = new PropertyChangeSupport(this);
    
    // 保存Service標簽下的Connector對象
    protected Connector connectors[] = new Connector[0];

    private final Object connectorsLock = new Object();
    
    // 保存Service的線程池Executor對象
    protected final ArrayList<Executor> executors = new ArrayList<>();
    
    // 保存Service的Engine對象
    private Engine engine = null;

    private ClassLoader parentClassLoader = null;

    protected final Mapper mapper = new Mapper();

    protected final MapperListener mapperListener = new MapperListener(this);

Engine - StandardEngine

? StandardEngine實現(xiàn)了Server接口和Lifecycle接口，核心變量在基類ContainerBase：

基類ContainerBase的HashMap<String, Container> children保存<Host>對應(yīng)的對象蜕琴。
基類ContainerBase的Realm realm對象保存<Realm>標簽對應(yīng)的對象萍桌。
基類ContainerBase的Pipeline pipeline保存調(diào)用鏈并保存Valve對象。

public class StandardEngine extends ContainerBase implements Engine {
    public StandardEngine() {

        super();
        // 省略相關(guān)代碼
    }

    private String defaultHost = null;

    private Service service = null;

    private String jvmRouteId;
}


public abstract class ContainerBase extends LifecycleMBeanBase implements Container {

    // 保存Host對象
    protected final HashMap<String, Container> children = new HashMap<>();

    protected int backgroundProcessorDelay = -1;

    protected final List<ContainerListener> listeners = new CopyOnWriteArrayList<>();

    protected Cluster cluster = null;

    private final ReadWriteLock clusterLock = new ReentrantReadWriteLock();

    protected String name = null;

    protected Container parent = null;

    protected ClassLoader parentClassLoader = null;

    protected final Pipeline pipeline = new StandardPipeline(this);
    // 保存Realm對象
    private volatile Realm realm = null;

    private final ReadWriteLock realmLock = new ReentrantReadWriteLock();

    protected boolean startChildren = true;

    private Thread thread = null;

    private volatile boolean threadDone = false;

    private int startStopThreads = 1;

    protected ThreadPoolExecutor startStopExecutor;
}

Host - StandardHost

? StandardEngine實現(xiàn)了Server接口和Lifecycle接口凌简，部分變量在基類ContainerBase：

appBase 變量保存Host標簽的appBase上炎。
autoDeploy 變量保存Host標簽的autoDeploy。
unpackWARs 變量保存Host標簽的unpackWARs雏搂。
基類ContainerBase的變量HashMap<String, Container> children保存Context變量藕施。
基類ContainerBase的Pipeline pipeline保存調(diào)用鏈并保存Valve對象。

public class StandardHost extends ContainerBase implements Host {

    public StandardHost() {

        super();
        pipeline.setBasic(new StandardHostValve());

    }

    private String[] aliases = new String[0];

    private final Object aliasesLock = new Object();

    private String appBase = "webapps";

    private volatile File appBaseFile = null;

    private String xmlBase = null;

    private volatile File hostConfigBase = null;

    private boolean autoDeploy = true;

    private String configClass = "org.apache.catalina.startup.ContextConfig";

    private String contextClass = "org.apache.catalina.core.StandardContext";

    private boolean deployOnStartup = true;

    private boolean deployXML = !Globals.IS_SECURITY_ENABLED;

    private boolean copyXML = false;

    private String errorReportValveClass = "org.apache.catalina.valves.ErrorReportValve";

    private boolean unpackWARs = true;

    private String workDir = null;

    private boolean createDirs = true;

    private final Map<ClassLoader, String> childClassLoaders = new WeakHashMap<>();

    private Pattern deployIgnore = null;

    private boolean undeployOldVersions = false;

    private boolean failCtxIfServletStartFails = false;
}



public abstract class ContainerBase extends LifecycleMBeanBase implements Container {

    // 保存Context對象
    protected final HashMap<String, Container> children = new HashMap<>();

    protected int backgroundProcessorDelay = -1;

    protected final List<ContainerListener> listeners = new CopyOnWriteArrayList<>();

    protected Cluster cluster = null;

    private final ReadWriteLock clusterLock = new ReentrantReadWriteLock();

    protected String name = null;

    protected Container parent = null;

    protected ClassLoader parentClassLoader = null;

    protected final Pipeline pipeline = new StandardPipeline(this);
    // 保存Realm對象
    private volatile Realm realm = null;

    private final ReadWriteLock realmLock = new ReentrantReadWriteLock();

    protected boolean startChildren = true;

    private Thread thread = null;

    private volatile boolean threadDone = false;

    private int startStopThreads = 1;

    protected ThreadPoolExecutor startStopExecutor;
}

Context - StandardContext

? StandardEngine實現(xiàn)了Server接口和Lifecycle接口凸郑，部分變量如下：

在context容器中可以定義非常多的屬性裳食，詳細內(nèi)容見官方手冊。
wrapperClass：實現(xiàn)wrapper容器的類芙沥，wrapper用于管理該context中的servlet胞谈，該類必須實現(xiàn)org.apache.catalina.Wrapper接口尘盼，如果不指定該屬性則采用默認的標準類。
基類ContainerBase的Pipeline pipeline保存調(diào)用鏈并保存Valve對象烦绳。

public class StandardContext extends ContainerBase implements Context, 
NotificationEmitter {

    // 省略相關(guān)代碼

    private String wrapperClassName = StandardWrapper.class.getName();
    private Class<?> wrapperClass = null;
}

Wrapper - StandardWrapper

?StandardWrapper實現(xiàn)了StandardWrapper接口用以處理servlet請求。

public class StandardWrapper extends ContainerBase
    implements StandardWrapper, Wrapper, NotificationEmitter {

    protected static final String[] DEFAULT_SERVLET_METHODS = 
                          new String[] {"GET", "HEAD", "POST" };


    public StandardWrapper() {

        super();
        swValve=new StandardWrapperValve();
        pipeline.setBasic(swValve);
        broadcaster = new NotificationBroadcasterSupport();

    }

    protected long available = 0L;
    protected final NotificationBroadcasterSupport broadcaster;
    protected final AtomicInteger countAllocated = new AtomicInteger(0);
    protected final StandardWrapperFacade facade = new StandardWrapperFacade(this);
    protected volatile Servlet instance = null;
    protected volatile boolean instanceInitialized = false;
    protected int loadOnStartup = -1;
    protected final ArrayList<String> mappings = new ArrayList<>();
    protected HashMap<String, String> parameters = new HashMap<>();
    protected HashMap<String, String> references = new HashMap<>();
    protected String runAs = null;
    protected long sequenceNumber = 0;
    protected String servletClass = null;
    protected volatile boolean singleThreadModel = false;
    protected volatile boolean unloading = false;
    protected int maxInstances = 20;
    protected int nInstances = 0;
    protected Stack<Servlet> instancePool = null;
    protected long unloadDelay = 2000;
    protected boolean isJspServlet;
    protected ObjectName jspMonitorON;
    protected boolean swallowOutput = false;
    protected StandardWrapperValve swValve;
    protected long loadTime=0;
    protected int classLoadTime=0;
    protected MultipartConfigElement multipartConfigElement = null;
    protected boolean asyncSupported = false;
    protected boolean enabled = true;
    private boolean overridable = false;

    protected static Class<?>[] classType = new Class[]{ServletConfig.class};

    private final ReentrantReadWriteLock parametersLock =
            new ReentrantReadWriteLock();
    private final ReentrantReadWriteLock mappingsLock =
            new ReentrantReadWriteLock();
    private final ReentrantReadWriteLock referencesLock =
            new ReentrantReadWriteLock();
}

Executor - StandardThreadExecutor

? Tomcat自定義Executor接口配紫，繼承自juc包下的Executor接口径密，增加getName()接口。

public interface Executor extends java.util.concurrent.Executor, Lifecycle {

    public String getName();

    void execute(Runnable command, long timeout, TimeUnit unit);
}

? Tomcat自定義ThreadPoolExecutor類躺孝，繼承自juc包下的ThreadPoolExecutor接口享扔，重寫execute()方法。

public class ThreadPoolExecutor extends java.util.concurrent.ThreadPoolExecutor {

    private final AtomicInteger submittedCount = new AtomicInteger(0);
    private final AtomicLong lastContextStoppedTime = new AtomicLong(0L);
    private final AtomicLong lastTimeThreadKilledItself = new AtomicLong(0L);

    private long threadRenewalDelay = Constants.DEFAULT_THREAD_RENEWAL_DELAY;

    public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, RejectedExecutionHandler handler) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, handler);
        prestartAllCoreThreads();
    }

    public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory,
            RejectedExecutionHandler handler) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
        prestartAllCoreThreads();
    }

    public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, new RejectHandler());
        prestartAllCoreThreads();
    }

    public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, new RejectHandler());
        prestartAllCoreThreads();
    }

    @Override
    public void execute(Runnable command) {
        execute(command,0,TimeUnit.MILLISECONDS);
    }

    public void execute(Runnable command, long timeout, TimeUnit unit) {
        submittedCount.incrementAndGet();
        try {
            super.execute(command);
        } catch (RejectedExecutionException rx) {
            if (super.getQueue() instanceof TaskQueue) {
                final TaskQueue queue = (TaskQueue)super.getQueue();
                try {
                    if (!queue.force(command, timeout, unit)) {
                        submittedCount.decrementAndGet();
                        throw new RejectedExecutionException("Queue capacity is full.");
                    }
                } catch (InterruptedException x) {
                    submittedCount.decrementAndGet();
                    throw new RejectedExecutionException(x);
                }
            } else {
                submittedCount.decrementAndGet();
                throw rx;
            }

        }
    }
}

? Tomcat的StandardThreadExecutor實現(xiàn)Lifecycle接口并實現(xiàn)自定義的Executor接口植袍。

StandardThreadExecutor的executor對象是自定義的ThreadPoolExecutor對象惧眠。
自定義的ThreadPoolExecutor對象是在startInternal()方法內(nèi)部初始化，自定義線程工廠以及任務(wù)隊列于个。
StandardThreadExecutor實現(xiàn)了自定義Executor接口并在execute()方法執(zhí)行自定義ThreadPoolExecutor的方法氛魁。

public class StandardThreadExecutor extends LifecycleMBeanBase
        implements Executor, ResizableExecutor {

    protected int threadPriority = Thread.NORM_PRIORITY;
    protected boolean daemon = true;
    protected String namePrefix = "tomcat-exec-";
    protected int maxThreads = 200;
    protected int minSpareThreads = 25;
    protected int maxIdleTime = 60000;
    protected ThreadPoolExecutor executor = null;
    protected String name;
    protected boolean prestartminSpareThreads = false;
    protected int maxQueueSize = Integer.MAX_VALUE;
    protected long threadRenewalDelay = org.apache.tomcat.util.threads.Constants.DEFAULT_THREAD_RENEWAL_DELAY;
    private TaskQueue taskqueue = null;

    public StandardThreadExecutor() {
        //empty constructor for the digester
    }


    @Override
    protected void initInternal() throws LifecycleException {
        super.initInternal();
    }

    @Override
    protected void startInternal() throws LifecycleException {

        taskqueue = new TaskQueue(maxQueueSize);
        TaskThreadFactory tf = new TaskThreadFactory(namePrefix,daemon,getThreadPriority());
        // 自定義ThreadPoolExecutor
        executor = new ThreadPoolExecutor(getMinSpareThreads(), getMaxThreads(), maxIdleTime, TimeUnit.MILLISECONDS,taskqueue, tf);
        executor.setThreadRenewalDelay(threadRenewalDelay);
        if (prestartminSpareThreads) {
            executor.prestartAllCoreThreads();
        }
        taskqueue.setParent(executor);

        setState(LifecycleState.STARTING);
    }

    @Override
    public void execute(Runnable command, long timeout, TimeUnit unit) {
        if ( executor != null ) {
            executor.execute(command,timeout,unit);
        } else {
            throw new IllegalStateException("StandardThreadExecutor not started.");
        }
    }


    @Override
    public void execute(Runnable command) {
        if ( executor != null ) {
            try {
                executor.execute(command);
            } catch (RejectedExecutionException rx) {
                //there could have been contention around the queue
                if ( !( (TaskQueue) executor.getQueue()).force(command) ) throw new RejectedExecutionException("Work queue full.");
            }
        } else throw new IllegalStateException("StandardThreadPool not started.");
    }
}

Connector & ProtocolHandler & AbstractEndpoint

? Connector的核心變量如下：

協(xié)議處理接口ProtocolHandler protocolHandler。
Coyote adapter 的 Adapter adapter厅篓。

public class Connector extends LifecycleMBeanBase  {

    public Connector() {
        this(null);
    }

    public Connector(String protocol) {
        setProtocol(protocol);

        ProtocolHandler p = null;
        try {
            Class<?> clazz = Class.forName(protocolHandlerClassName);
            p = (ProtocolHandler) clazz.getConstructor().newInstance();
        } catch (Exception e) {
            log.error(sm.getString(
                    "coyoteConnector.protocolHandlerInstantiationFailed"), e);
        } finally {
            this.protocolHandler = p;
        }

    protected Service service = null;
    protected boolean allowTrace = false;
    protected long asyncTimeout = 30000;
    protected boolean enableLookups = false;
    protected boolean xpoweredBy = false;
    protected int port = -1;
    protected String proxyName = null;
    protected int proxyPort = 0;
    protected int redirectPort = 443;
    protected String scheme = "http";
    protected boolean secure = false;
    private int maxCookieCount = 200;
    protected int maxParameterCount = 10000;
    protected int maxPostSize = 2 * 1024 * 1024;
    protected int maxSavePostSize = 4 * 1024;
    protected String parseBodyMethods = "POST";
    protected HashSet<String> parseBodyMethodsSet;
    protected boolean useIPVHosts = false;
    protected String protocolHandlerClassName =
        "org.apache.coyote.http11.Http11NioProtocol";

    // 協(xié)議處理接口 Coyote protocol handler.
    protected final ProtocolHandler protocolHandler;
    // Coyote adapter.
    protected Adapter adapter = null;

    protected String URIEncoding = null;
    protected String URIEncodingLower = null;
    private Charset uriCharset = StandardCharsets.UTF_8;
    protected boolean useBodyEncodingForURI = false;


    protected static final HashMap<String,String> replacements = new HashMap<>();
    static {
        replacements.put("acceptCount", "backlog");
        replacements.put("connectionLinger", "soLinger");
        replacements.put("connectionTimeout", "soTimeout");
        replacements.put("rootFile", "rootfile");
    }
}

? ProtocolHandler的核心變量如下：

ProtocolHandler的內(nèi)部包含AbstractEndpoint<S> endpoint負責監(jiān)聽連接秀存。

public abstract class AbstractProtocol<S> implements ProtocolHandler,
        MBeanRegistration {

    private static final StringManager sm = StringManager.getManager(AbstractProtocol.class);

    private static final AtomicInteger nameCounter = new AtomicInteger(0);

    protected ObjectName rgOname = null;

    private int nameIndex = 0;

    private final AbstractEndpoint<S> endpoint;

    private Handler<S> handler;

    private final Set<Processor> waitingProcessors =
            Collections.newSetFromMap(new ConcurrentHashMap<Processor, Boolean>());

    private AsyncTimeout asyncTimeout = null;
}

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