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：
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：
- play.Play类：代表Play本身业务模型。
- play.server.Server类：负责服务器启动。
- 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：
- Play.init
- 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：
- 加载配置
- 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
- 加载route
- 加载Module，Play的应用扩展组件。
- 加载Plugin，Play框架自身的扩展组件。
- 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：
- plugin.compileAll，给所有plugin一次机会进行自定义编译。
- 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。
- loadApplicationClass，取出ApplicationClass中的.class加入List<Class>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：
- 设置端口，地址
- 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。
- 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。
- bootstrap.bind(new InetSocketAddress(address, httpPort)，绑定地址，端口。
到此万事具备，只等东风了…