上节讲到的JDK自带的HttpServer组件，实现方法大概有三十个类构成，下面尝试着理解下实现思路。
由于Java的source代码中有很多注释，粘贴上来看着费劲，自己写个程序消除注释。
import java.io.BufferedReader;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStreamReader;/** * @author 作者 E-mail: * @version 创建时间：2015-10-30 下午02:38:17 类说明 处理从JDK当中的注释 */public class Test{ public static void main(String[] args) throws IOException { FileInputStream inputStream = new FileInputStream("source"); FileOutputStream outputStream = new FileOutputStream("res"); BufferedReader br = new BufferedReader(new InputStreamReader(inputStream)); final StringBuilder builder = new StringBuilder(); String tempstr = null; while ((tempstr = br.readLine()) != null) { if (tempstr.indexOf('*') == -1) { builder.append(tempstr + '\n'); } } outputStream.write(builder.toString().getBytes("gbk")); }} com.sun.net.httpserver包下的类和接口提供了一系列的标准
sun.net.httpserver包下类根据标准做了一系列的实现
com.sun.net.httpserver.HttpServer.java
package com.sun.net.httpserver;import com.sun.net.httpserver.spi.HttpServerProvider;public abstract class HttpServer { protected HttpServer () { } //默认创建HttpServer对象 public static HttpServer create () throws IOException { return create (null, 0); } //根据InetSocketAddress对象和backlog对象创建HttpServer对象 public static HttpServer create (InetSocketAddress addr, int backlog) throws IOException { //HttpServer实例的服务提供者HttpServerProvider HttpServerProvider provider = HttpServerProvider.provider(); //由服务提供者创建HttpServer对象 return provider.createHttpServer (addr, backlog); } //绑定网络地址接口 public abstract void bind (InetSocketAddress addr, int backlog) throws IOException; //启动httpServer接口 public abstract void start () ; //设置线程池 public abstract void setExecutor (Executor executor); public abstract Executor getExecutor () ; public abstract void stop (int delay); //指定url和相应的处理Handler public abstract HttpContext createContext (String path, HttpHandler handler) ; public abstract HttpContext createContext (String path) ; public abstract void removeContext (String path) throws IllegalArgumentException ; public abstract void removeContext (HttpContext context) ; public abstract InetSocketAddress getAddress() ;}
com.sun.net.httpserver.spi.HttpServerProvider
package com.sun.net.httpserver.spi;import java.io.FileDescriptor;import java.io.IOException;import java.security.AccessController;import java.security.PrivilegedAction;import java.util.Iterator;import sun.misc.Service;import sun.misc.ServiceConfigurationError;import sun.security.action.GetPropertyAction;public abstract class HttpServerProvider { public abstract HttpServer createHttpServer (InetSocketAddress addr, int backlog) throws IOException; public abstract HttpsServer createHttpsServer (InetSocketAddress addr, int backlog) throws IOException; private static final Object lock = new Object(); private static HttpServerProvider provider = null; protected HttpServerProvider() { SecurityManager sm = System.getSecurityManager(); if (sm != null) sm.checkPermission(new RuntimePermission("httpServerProvider")); } private static boolean loadProviderFromProperty() { String cn = System.getProperty("com.sun.net.httpserver.HttpServerProvider"); if (cn == null) return false; try { Class c = Class.forName(cn, true, ClassLoader.getSystemClassLoader()); provider = (HttpServerProvider)c.newInstance(); return true; } catch (ClassNotFoundException x) { throw new ServiceConfigurationError(x); } catch (IllegalAccessException x) { throw new ServiceConfigurationError(x); } catch (InstantiationException x) { throw new ServiceConfigurationError(x); } catch (SecurityException x) { throw new ServiceConfigurationError(x); } } private static boolean loadProviderAsService() { Iterator i = Service.providers(HttpServerProvider.class, ClassLoader.getSystemClassLoader()); for (;;) { try { if (!i.hasNext()) return false; provider = (HttpServerProvider)i.next(); return true; } catch (ServiceConfigurationError sce) { if (sce.getCause() instanceof SecurityException) { // Ignore the security exception, try the next provider continue; } throw sce; } } } public static HttpServerProvider provider () { synchronized (lock) { if (provider != null) return provider; return (HttpServerProvider)AccessController .doPrivileged(new PrivilegedAction
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上面说到com.sun.net.httpServer包下类和接口都是提供了一套标准，应用程序使用API的时候只关心这套标准，具体标准的实现应用程序是不关心的，实现了应用程序开发者和服务提供者的解耦，服务提供者可以提供多种多样的实现。
对于同一个功能，不同的厂家会提供不同的产品，比如不同品牌的轮胎、插头等。在软件行业，情况也是如此。比如，对于数据的加密解密，不同的厂家使用不同的算法，提供强度各异的不同软件包。应用软件根据不同的开发需求，往往需要使用不同的软件包。每次更换不同的软件包，都会重复以下过程：更改应用软件代码 -> 重新编译 -> 测试 -> 部署。这种做法一般被称为开发时绑定。这其实是一种比较原始的做法，缺乏灵活性和开放性。于是应用运行时绑定服务提供者的做法流行开来。具体做法是，使用配置文件指定，然后在运行时载入具体实现。 SE 平台提供的 Service Provider 机制是折衷了开发时绑定和运行时绑定两种方式，很好的满足了高效和开放两个要求。
构成一个 Service Provider 框架需要大致三个部分，图 1 给出了一个典型的 Service Provider 组件结构。 SE 平台的大部分 Service Provider 框架都提供了 3 个主要个组件：面向开发者的 Application 接口，面向服务提供商的 Service Provider 接口和真正的服务提供者。
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重点关注Application接口的两个方法
com.sun.net.httpServer.HttpServer.java
方法作用：
创建一个HttpServer实例，该实例绑定于一个确定的网络地址(由IP地址和端口号组成)
指定一个最大的监听backlog的长度，这个长度是指允许在这个监听Socket上排队等待连接的最大数量。该HttpServer实例来自于当前的HttpServerProvider
/** * Create aHttpServerinstance which will bind to the * specified {@link java.net.InetSocketAddress} (IP address and port number) * * A maximum backlog can also be specified. This is the maximum number of * queued incoming connections to allow on the listening socket. * Queued TCP connections exceeding this limit may be rejected by the TCP implementation. * The HttpServer is acquired from the currently installed {@link HttpServerProvider} * * @param addr the address to listen on, ifnullthen bind() must be called * to set the address * @param backlog the socket backlog. If this value is less than or equal to zero, * then a system default value is used. * @throws BindException if the server cannot bind to the requested address, * or if the server is already bound. * @throws IOException */ public static HttpServer create ( InetSocketAddress addr, int backlog ) throws IOException { HttpServerProvider provider = HttpServerProvider.provider(); return provider.createHttpServer (addr, backlog); }
这个模式和JAXP获取XML解析对象的过程很像
com.sun.net.httpServer.HttpServerProvider.java
方法作用：
针对JVM的请求返回系统的HttpServerProvider，查找过程
1：如果系统属性(system property) com.sun.net.httpserver.HttpServerProvider被定义过，找到相应的类
private static boolean loadProviderFromProperty() { String cn = System.getProperty("com.sun.net.httpserver.HttpServerProvider"); if (cn == null) return false; try { Class c = Class.forName(cn, true, ClassLoader.getSystemClassLoader()); provider = (HttpServerProvider)c.newInstance(); return true; } catch (ClassNotFoundException x) { throw new ServiceConfigurationError(x); } catch (IllegalAccessException x) { throw new ServiceConfigurationError(x); } catch (InstantiationException x) { throw new ServiceConfigurationError(x); } catch (SecurityException x) { throw new ServiceConfigurationError(x); } }
2:第三方jar包的属性文件当中是否有相应设置
查找所有加载的jar包中META-INF/services目录下的配置文件，文件名为
private static boolean loadProviderAsService() { Iterator i = Service.providers(HttpServerProvider.class,ClassLoader.getSystemClassLoader()); for (;;) { try { if (!i.hasNext()) return false; provider = (HttpServerProvider)i.next(); return true; } catch (ServiceConfigurationError sce) { if (sce.getCause() instanceof SecurityException) { // Ignore the security exception, try the next provider continue; } throw sce; } } } sun.misc.Service.java
/** * Locates and incrementally instantiates the available providers of a * given service using the given class loader. * *This method transforms the name of the given service class into a * provider-configuration filename as described above and then uses the * getResources method of the given class loader to find all * available files with that name. These files are then read and parsed to * produce a list of provider-class names. The iterator that is returned * uses the given class loader to lookup and then instantiate each element * of the list. * *
Because it is possible for extensions to be installed into a running * Java virtual machine, this method may return different results each time * it is invoked.
* * @param service * The service's abstract service class * * @param loader * The class loader to be used to load provider-configuration files * and instantiate provider classes, or null if the system * class loader (or, failing that the bootstrap class loader) is to * be used * * @return An Iterator that yields provider objects for the given * service, in some arbitrary order. The iterator will throw a * ServiceConfigurationError if a provider-configuration * file violates the specified format or if a provider class cannot * be found and instantiated. * * @throws ServiceConfigurationError * If a provider-configuration file violates the specified format * or names a provider class that cannot be found and instantiated * * @see #providers(java.lang.Class) * @see #installedProviders(java.lang.Class) */ public static Iterator providers(Class service, ClassLoader loader) throws ServiceConfigurationError { return new LazyIterator(service, loader); }
Service.java下面的内部类
/** * Private inner class implementing fully-lazy provider lookup */ private static class LazyIterator implements Iterator { Class service; ClassLoader loader; Enumeration configs = null; Iterator pending = null; Set returned = new TreeSet(); String nextName = null; private LazyIterator(Class service, ClassLoader loader) { this.service = service; this.loader = loader; } public boolean hasNext() throws ServiceConfigurationError { if (nextName != null) { return true; } if (configs == null) { try { String fullName = prefix + service.getName(); if (loader == null) configs = ClassLoader.getSystemResources(fullName); else configs = loader.getResources(fullName); } catch (IOException x) { fail(service, ": " + x); } } while ((pending == null) || !pending.hasNext()) { if (!configs.hasMoreElements()) { return false; } pending = parse(service, (URL)configs.nextElement(), returned); } nextName = (String)pending.next(); return true; } public Object next() throws ServiceConfigurationError { if (!hasNext()) { throw new NoSuchElementException(); } String cn = nextName; nextName = null; try { return Class.forName(cn, true, loader).newInstance(); } catch (ClassNotFoundException x) { fail(service, "Provider " + cn + " not found"); } catch (Exception x) { fail(service, "Provider " + cn + " could not be instantiated: " + x, x); } return null; /* This cannot happen */ } public void remove() { throw new UnsupportedOperationException(); } }
/** * Returns the system wide default HttpServerProvider for this invocation of * the Java virtual machine. * *The first invocation of this method locates the default provider * object as follows:
* ** *
* *- * *
If the system property * com.sun.net.httpserver.HttpServerProvider is defined then it is * taken to be the fully-qualified name of a concrete provider class. * The class is loaded and instantiated; if this process fails then an * unspecified unchecked error or exception is thrown.
- * *
If a provider class has been installed in a jar file that is * visible to the system class loader, and that jar file contains a * provider-configuration file named * com.sun.net.httpserver.HttpServerProvider in the resource * directory META-INF/services, then the first class name * specified in that file is taken. The class is loaded and * instantiated; if this process fails then an unspecified unchecked error or exception is * thrown.
- * *
Finally, if no provider has been specified by any of the above * means then the system-default provider class is instantiated and the * result is returned.
Subsequent invocations of this method return the provider that was * returned by the first invocation.
* * @return The system-wide default HttpServerProvider */ public static HttpServerProvider provider () { synchronized (lock) { if (provider != null) return provider; return (HttpServerProvider)AccessController .doPrivileged(new PrivilegedAction
最终如果前两种方法都没有找到相应的HttpServerProvider实例，则使用sun公司为我们提供的HttpServerProvider实例
sun.net.httpserver.DefaultHttpServerProvider类
也就是我们通常使用的类。
sun.net.httpserver.DefaultHttpServerProvider类
package sun.net.httpserver;import java.net.*;import java.io.*;import com.sun.net.httpserver.*;import com.sun.net.httpserver.spi.*;public class DefaultHttpServerProvider extends HttpServerProvider { public HttpServer createHttpServer (InetSocketAddress addr, int backlog) throws IOException { return new HttpServerImpl (addr, backlog); } public HttpsServer createHttpsServer (InetSocketAddress addr, int backlog) throws IOException { return new HttpsServerImpl (addr, backlog); }} sun.net.httpserver.HttpServerImpl类 （其实还有HTTPS的实现类，这里先不讲）
package sun.net.httpserver;import java.net.*;import java.io.*;import java.nio.*;import java.security.*;import java.nio.channels.*;import java.util.*;import java.util.concurrent.*;import javax.net.ssl.*;import com.sun.net.httpserver.*;import com.sun.net.httpserver.spi.*;public class HttpServerImpl extends HttpServer { ServerImpl server; HttpServerImpl () throws IOException { this (new InetSocketAddress(80), 0); } HttpServerImpl ( InetSocketAddress addr, int backlog ) throws IOException { server = new ServerImpl (this, "http", addr, backlog); } public void bind (InetSocketAddress addr, int backlog) throws IOException { server.bind (addr, backlog); } public void start () { server.start(); } public void setExecutor (Executor executor) { server.setExecutor(executor); } public Executor getExecutor () { return server.getExecutor(); } public void stop (int delay) { server.stop (delay); } public HttpContextImpl createContext (String path, HttpHandler handler) { return server.createContext (path, handler); } public HttpContextImpl createContext (String path) { return server.createContext (path); } public void removeContext (String path) throws IllegalArgumentException { server.removeContext (path); } public void removeContext (HttpContext context) throws IllegalArgumentException { server.removeContext (context); } public InetSocketAddress getAddress() { return server.getAddress(); }}