Play源代码分析1—Server启动过程

Play源代码分析1—Server启动过程

Play是个Rails风格的Java Web框架，需要了解背景请看：

1. Play Framework介绍1--主要概念
2. Play Framework介绍2—Helloworld

如何调试请看此处。以下进入正题^_^

Server启动过程主要涉及三个地方：

1. play.Play类：代表Play本身业务模型。
2. play.server.Server类：负责服务器启动。
3. play.classloading包：负责.java文件读取、编译和加载。

总体流程：

Server.main为入口方法：

   
   
   
   

    
    
    
    public
    
    
    
     
    
    
    
    static
    
    
    
     
    
    
    
    void
    
    
    
     main(String[] args) 
    
    
    
    throws
    
    
    
     Exception {
 …
 Play.init(root, System.getProperty(
    
    
    
    "
    
    
    
    play.id
    
    
    
    "
    
    
    
    , 
    
    
    
    ""
    
    
    
    ));
 
    
    
    
    if
    
    
    
     (System.getProperty(
    
    
    
    "
    
    
    
    precompile
    
    
    
    "
    
    
    
    ) 
    
    
    
    ==
    
    
    
     
    
    
    
    null
    
    
    
    ) {
 
    
    
    
    new
    
    
    
     Server();
 } 
    
    
    
    else
    
    
    
     {
 Logger.info(
    
    
    
    "
    
    
    
    Done.
    
    
    
    "
    
    
    
    );
 }
 }
   
   
   
   

 

做两件事：

1. Play.init
2. 然后创建Server对象。

Play.init

   
   
   
   

    
    
    
    public
    
    
    
     
    
    
    
    static
    
    
    
     
    
    
    
    void
    
    
    
     init(File root, String id) {
 
 …
 
 readConfiguration();
 
 Play.classes 
    
    
    
    =
    
    
    
     
    
    
    
    new
    
    
    
     ApplicationClasses();
 
 …
 
 
    
    
    
    //
    
    
    
     Build basic java source path
    
    
    
    
 
    
    
    
     VirtualFile appRoot 
    
    
    
    =
    
    
    
     VirtualFile.open(applicationPath);
 roots.add(appRoot);
 javaPath 
    
    
    
    =
    
    
    
     
    
    
    
    new
    
    
    
     ArrayList
    
    
    
    <
    
    
    
    VirtualFile
    
    
    
    >
    
    
    
    (
    
    
    
    2
    
    
    
    );
 javaPath.add(appRoot.child(
    
    
    
    "
    
    
    
    app
    
    
    
    "
    
    
    
    ));
 javaPath.add(appRoot.child(
    
    
    
    "
    
    
    
    conf
    
    
    
    "
    
    
    
    ));
 
 
    
    
    
    //
    
    
    
     Build basic templates path
    
    
    
    
 
    
    
    
     templatesPath 
    
    
    
    =
    
    
    
     
    
    
    
    new
    
    
    
     ArrayList
    
    
    
    <
    
    
    
    VirtualFile
    
    
    
    >
    
    
    
    (
    
    
    
    2
    
    
    
    );
 templatesPath.add(appRoot.child(
    
    
    
    "
    
    
    
    app/views
    
    
    
    "
    
    
    
    ));
 
 
    
    
    
    //
    
    
    
     Main route file
    
    
    
    
 
    
    
    
     routes 
    
    
    
    =
    
    
    
     appRoot.child(
    
    
    
    "
    
    
    
    conf/routes
    
    
    
    "
    
    
    
    );
 
 …
 
 
    
    
    
    //
    
    
    
     Load modules
    
    
    
    
 
    
    
    
     loadModules();
 
 …
 
 
    
    
    
    //
    
    
    
     Enable a first classloader
    
    
    
    
 
    
    
    
     classloader 
    
    
    
    =
    
    
    
     
    
    
    
    new
    
    
    
     ApplicationClassloader();
 
 
    
    
    
    //
    
    
    
     Plugins
    
    
    
    
 
    
    
    
     loadPlugins();
 
 
    
    
    
    //
    
    
    
     Done !
    
    
    
    
 
    
    
    
     
    
    
    
    if
    
    
    
     (mode 
    
    
    
    ==
    
    
    
     Mode.PROD 
    
    
    
    ||
    
    
    
    preCompile() ) {
 start();
 }
 
 …
 }
   
   
   
   

 

主要做：

1. 加载配置
2. new ApplicationClasses();加载app、views和conf路径到VirtualFile中，VirtualFile是Play内部的统一文件访问接口，方便后续读取文件
3. 加载route
4. 加载Module，Play的应用扩展组件。
5. 加载Plugin，Play框架自身的扩展组件。
6. 工作在产品模式则启动Play.

关键步骤为new ApplicationClasses(),执行computeCodeHashe(),后者触发目录扫描，搜索.java文件。相关过程简化代码如下：

   
   
   
   

    
    
    
    public
    
    
    
     ApplicationClassloader() {
 
    
    
    
    super
    
    
    
    (ApplicationClassloader.
    
    
    
    class
    
    
    
    .getClassLoader());
 
    
    
    
    //
    
    
    
     Clean the existing classes
    
    
    
    
 
    
    
    
     
    
    
    
    for
    
    
    
     (ApplicationClass applicationClass : Play.classes.all()) {
 applicationClass.uncompile();
 }
 pathHash 
    
    
    
    =
    
    
    
     computePathHash();
 …
 }
   
   
   
   

   
   
   
   

    
    
    
    int
    
    
    
     computePathHash() {
 StringBuffer buf 
    
    
    
    =
    
    
    
     
    
    
    
    new
    
    
    
     StringBuffer();
 
    
    
    
    for
    
    
    
     (VirtualFile virtualFile : Play.javaPath) {
 scan(buf, virtualFile);
 }
 
    
    
    
    return
    
    
    
     buf.toString().hashCode();
 }
   
   
   
   

   
   
   
   

    
    
    
     
    
    
    
    void
    
    
    
     scan(StringBuffer buf, VirtualFile current) {
 
    
    
    
    if
    
    
    
     (
    
    
    
    !
    
    
    
    current.isDirectory()) {
 
    
    
    
    if
    
    
    
     (current.getName().endsWith(
    
    
    
    "
    
    
    
    .java
    
    
    
    "
    
    
    
    )) {
 Matcher matcher 
    
    
    
    =
    
    
    
     Pattern.compile(
    
    
    
    "
    
    
    
    \\s+class\\s([a-zA-Z0-9_]+)\\s+
    
    
    
    "
    
    
    
    ).matcher(current.contentAsString());
 buf.append(current.getName());
 buf.append(
    
    
    
    "
    
    
    
    (
    
    
    
    "
    
    
    
    );
 
    
    
    
    while
    
    
    
     (matcher.find()) {
 buf.append(matcher.group(
    
    
    
    1
    
    
    
    ));
 buf.append(
    
    
    
    "
    
    
    
    ,
    
    
    
    "
    
    
    
    );
 }
 buf.append(
    
    
    
    "
    
    
    
    )
    
    
    
    "
    
    
    
    );
 }
 } 
    
    
    
    else
    
    
    
     
    
    
    
    if
    
    
    
     (
    
    
    
    !
    
    
    
    current.getName().startsWith(
    
    
    
    "
    
    
    
    .
    
    
    
    "
    
    
    
    )) {
 
    
    
    
    for
    
    
    
     (VirtualFile virtualFile : current.list()) {
 scan(buf, virtualFile);
 }
 }
 }
   
   
   
   

Start流程

简化代码如下：

   
   
   
   

    
    
    
    public
    
    
    
     
    
    
    
    static
    
    
    
     
    
    
    
    synchronized
    
    
    
     
    
    
    
    void
    
    
    
     start() {
 
    
    
    
    try
    
    
    
     {
 ...
 
    
    
    
    //
    
    
    
     Reload configuration
    
    
    
    
 
    
    
    
     readConfiguration();
 
 ...
 
 
    
    
    
    //
    
    
    
     Try to load all classes
    
    
    
    
 
    
    
    
     Play.classloader.getAllClasses();
 
 
    
    
    
    //
    
    
    
     Routes
    
    
    
    
 
    
    
    
     Router.detectChanges(ctxPath);
 
 
    
    
    
    //
    
    
    
     Cache
    
    
    
    
 
    
    
    
     Cache.init();
 
 
    
    
    
    //
    
    
    
     Plugins
    
    
    
    
 
    
    
    
     
    
    
    
    for
    
    
    
     (PlayPlugin plugin : plugins) {
 
    
    
    
    try
    
    
    
     {
 plugin.onApplicationStart();
 } 
    
    
    
    catch
    
    
    
    (Exception e) {
 
    
    
    
    if
    
    
    
    (Play.mode.isProd()) {
 Logger.error(e, 
    
    
    
    "
    
    
    
    Can't start in PROD mode with errors
    
    
    
    "
    
    
    
    );
 }
 
    
    
    
    if
    
    
    
    (e 
    
    
    
    instanceof
    
    
    
     RuntimeException) {
 
    
    
    
    throw
    
    
    
     (RuntimeException)e;
 }
 
    
    
    
    throw
    
    
    
     
    
    
    
    new
    
    
    
     UnexpectedException(e);
 }
 }
 
 ...
 
 
    
    
    
    //
    
    
    
     Plugins
    
    
    
    
 
    
    
    
     
    
    
    
    for
    
    
    
     (PlayPlugin plugin : plugins) {
 plugin.afterApplicationStart();
 }
 
 } 
    
    
    
    catch
    
    
    
     (PlayException e) {
 started 
    
    
    
    =
    
    
    
     
    
    
    
    false
    
    
    
    ;
 
    
    
    
    throw
    
    
    
     e;
 } 
    
    
    
    catch
    
    
    
     (Exception e) {
 started 
    
    
    
    =
    
    
    
     
    
    
    
    false
    
    
    
    ;
 
    
    
    
    throw
    
    
    
     
    
    
    
    new
    
    
    
     UnexpectedException(e);
 }
 }
   
   
   
   

关键步骤为执行Play.classloader.getAllClasses()加载app目录中的类型。简化代码如下：

   
   
   
   

    
    
    
    public
    
    
    
     List
    
    
    
    <
    
    
    
    Class
    
    
    
    >
    
    
    
     getAllClasses() {
 
    
    
    
    if
    
    
    
     (allClasses 
    
    
    
    ==
    
    
    
     
    
    
    
    null
    
    
    
    ) {
 allClasses 
    
    
    
    =
    
    
    
     
    
    
    
    new
    
    
    
     ArrayList
    
    
    
    <
    
    
    
    Class
    
    
    
    >
    
    
    
    ();
 
 
    
    
    
    if
    
    
    
     (Play.usePrecompiled) {
 ...
 } 
    
    
    
    else
    
    
    
     {
 List
    
    
    
    <
    
    
    
    ApplicationClass
    
    
    
    >
    
    
    
     all 
    
    
    
    =
    
    
    
     
    
    
    
    new
    
    
    
     ArrayList
    
    
    
    <
    
    
    
    ApplicationClass
    
    
    
    >
    
    
    
    ();
 
 
    
    
    
    //
    
    
    
     Let's plugins play
    
    
    
    
 
    
    
    
     
    
    
    
    for
    
    
    
     (PlayPlugin plugin : Play.plugins) {
 plugin.compileAll(all);
 }
 
 
    
    
    
    for
    
    
    
     (VirtualFile virtualFile : Play.javaPath) {
 all.addAll(getAllClasses(virtualFile));
 }
 List
    
    
    
    <
    
    
    
    String
    
    
    
    >
    
    
    
     classNames 
    
    
    
    =
    
    
    
     
    
    
    
    new
    
    
    
     ArrayList
    
    
    
    <
    
    
    
    String
    
    
    
    >
    
    
    
    ();
 
    
    
    
    for
    
    
    
     (
    
    
    
    int
    
    
    
     i 
    
    
    
    =
    
    
    
     
    
    
    
    0
    
    
    
    ; i 
    
    
    
    <
    
    
    
     all.size(); i
    
    
    
    ++
    
    
    
    ) {
 
    
    
    
    if
    
    
    
     (all.get(i) 
    
    
    
    !=
    
    
    
     
    
    
    
    null
    
    
    
     
    
    
    
    &&
    
    
    
     
    
    
    
    !
    
    
    
    all.get(i).compiled) {
 classNames.add(all.get(i).name);
 }
 }
 
 Play.classes.compiler.compile(classNames.toArray(
    
    
    
    new
    
    
    
     String[classNames.size()]));
 
 
    
    
    
    for
    
    
    
     (ApplicationClass applicationClass : Play.classes.all()) {
 Class clazz 
    
    
    
    =
    
    
    
     loadApplicationClass(applicationClass.name);
 
    
    
    
    if
    
    
    
     (clazz 
    
    
    
    !=
    
    
    
     
    
    
    
    null
    
    
    
    ) {
 allClasses.add(clazz);
 }
 }
 ...
 }
 }
 
    
    
    
    return
    
    
    
     allClasses;
 }
   
   
   
   

主要步骤：

1. plugin.compileAll，给所有plugin一次机会进行自定义编译。
2. Play.classes.compiler.compile(classNames.toArray(new String[classNames.size()]));编译所有.java文件。编译后的.class存储在ApplicationClass中。内部使用了eclipse的JDT编译器。
3. loadApplicationClass，取出ApplicationClass中的.class加入List中返回。

到此完成.java的加载。相关对象关系如下图：

接着new Server()启动HTTP服务，监听请求

简化代码如下：

   
   
   
   

    
    
    
    public
    
    
    
     Server() {
 ...
 
    
    
    
    if
    
    
    
     (httpPort 
    
    
    
    ==
    
    
    
     
    
    
    
    -
    
    
    
    1
    
    
    
     
    
    
    
    &&
    
    
    
     httpsPort 
    
    
    
    ==
    
    
    
     
    
    
    
    -
    
    
    
    1
    
    
    
    ) {
 httpPort 
    
    
    
    =
    
    
    
     
    
    
    
    9000
    
    
    
    ;
 }
 ...
 InetAddress address 
    
    
    
    =
    
    
    
     
    
    
    
    null
    
    
    
    ;
 
    
    
    
    try
    
    
    
     {
 
    
    
    
    if
    
    
    
     (p.getProperty(
    
    
    
    "
    
    
    
    http.address
    
    
    
    "
    
    
    
    ) 
    
    
    
    !=
    
    
    
     
    
    
    
    null
    
    
    
    ) {
 address 
    
    
    
    =
    
    
    
     InetAddress.getByName(p.getProperty(
    
    
    
    "
    
    
    
    http.address
    
    
    
    "
    
    
    
    ));
 } 
    
    
    
    else
    
    
    
     
    
    
    
    if
    
    
    
     (System.getProperties().containsKey(
    
    
    
    "
    
    
    
    http.address
    
    
    
    "
    
    
    
    )) {
 address 
    
    
    
    =
    
    
    
     InetAddress.getByName(System.getProperty(
    
    
    
    "
    
    
    
    http.address
    
    
    
    "
    
    
    
    ));
 }
 
 } 
    
    
    
    catch
    
    
    
     (Exception e) {
 Logger.error(e, 
    
    
    
    "
    
    
    
    Could not understand http.address
    
    
    
    "
    
    
    
    );
 System.exit(
    
    
    
    -
    
    
    
    1
    
    
    
    );
 }
 
 ServerBootstrap bootstrap 
    
    
    
    =
    
    
    
     
    
    
    
    new
    
    
    
     ServerBootstrap(
    
    
    
    new
    
    
    
     NioServerSocketChannelFactory(
 Executors.newCachedThreadPool(), Executors.newCachedThreadPool())
 );
 
    
    
    
    try
    
    
    
     {
 
    
    
    
    if
    
    
    
     (httpPort 
    
    
    
    !=
    
    
    
     
    
    
    
    -
    
    
    
    1
    
    
    
    ) {
 bootstrap.setPipelineFactory(
    
    
    
    new
    
    
    
     HttpServerPipelineFactory());
 bootstrap.bind(
    
    
    
    new
    
    
    
     InetSocketAddress(address, httpPort));
 bootstrap.setOption(
    
    
    
    "
    
    
    
    child.tcpNoDelay
    
    
    
    "
    
    
    
    , 
    
    
    
    true
    
    
    
    );
 
 
    
    
    
    if
    
    
    
     (Play.mode 
    
    
    
    ==
    
    
    
     Mode.DEV) {
 
    
    
    
    if
    
    
    
     (address 
    
    
    
    ==
    
    
    
     
    
    
    
    null
    
    
    
    ) {
 Logger.info(
    
    
    
    "
    
    
    
    Listening for HTTP on port %s (Waiting a first request to start) ...
    
    
    
    "
    
    
    
    , httpPort);
 } 
    
    
    
    else
    
    
    
     {
 Logger.info(
    
    
    
    "
    
    
    
    Listening for HTTP at %2$s:%1$s (Waiting a first request to start) ...
    
    
    
    "
    
    
    
    , httpPort, address);
 }
 } 
    
    
    
    else
    
    
    
     {
 
    
    
    
    if
    
    
    
     (address 
    
    
    
    ==
    
    
    
     
    
    
    
    null
    
    
    
    ) {
 Logger.info(
    
    
    
    "
    
    
    
    Listening for HTTP on port %s ...
    
    
    
    "
    
    
    
    , httpPort);
 } 
    
    
    
    else
    
    
    
     {
 Logger.info(
    
    
    
    "
    
    
    
    Listening for HTTP at %2$s:%1$s ...
    
    
    
    "
    
    
    
    , httpPort, address);
 }
 }
 
 }
 
 } 
    
    
    
    catch
    
    
    
     (ChannelException e) {
 Logger.error(
    
    
    
    "
    
    
    
    Could not bind on port 
    
    
    
    "
    
    
    
     
    
    
    
    +
    
    
    
     httpPort, e);
 System.exit(
    
    
    
    -
    
    
    
    1
    
    
    
    );
 }
 ...
 }
   
   
   
   

主要步骤：

1. 设置端口，地址
2. new ServerBootstrap，创建jboss netty服务器。Play1.1.1使用了netty作为底层通讯服务器。
3. new HttpServerPipelineFactory(),设置netty所需的请求处理管道工厂。它负责当请求到达时提供处理者。
4. bootstrap.bind(new InetSocketAddress(address, httpPort)，绑定地址，端口。

  

到此万事具备，只等东风了…