jdk6新特性

JDK6.0发布有段时间了，新的JDK也有不少新的特性，我去网上搜集了一下，列在下面和大家一起学习．
１．Desktop和SystemTray. 在JDK6中 ,AWT新增加了两个类:Desktop和SystemTray,前者可以用来打开系统默认浏览器浏览指定的URL,打开系统默认邮件客户端给指定的邮箱发邮件,用默认应用程序打开或编辑文件(比如,用记事本打开以txt为后缀名的文件),用系统默认的打印机打印文档;后者可以用来在系统托盘区创建一个托盘程序。

我随便找了几张图，在Tray里面都是空的，没有图,可能是图太大，有xdjm知道希望告诉我．


import java.awt.AWTException;
import java.awt.Desktop;
import java.awt.Image;
import java.awt.MenuItem;
import java.awt.PopupMenu;
import java.awt.SystemTray;
import java.awt.Toolkit;
import java.awt.TrayIcon;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;

public class DesktopTrayTest ...{
    private static Desktop desktop;
    private static SystemTray st;
    private static PopupMenu pm;
   
    public static void main( String[] args ) ...{
        if( Desktop.isDesktopSupported() ) ...{
            desktop = Desktop.getDesktop();
        }
        if( SystemTray.isSupported() ) ...{
            st = SystemTray.getSystemTray();
            Image image = Toolkit.getDefaultToolkit().createImage( "http://www.51ppt.com.cn/Article/Uploadphotos/200604/20064147333288.png" );
            createPopupMenu();
            TrayIcon ti = new TrayIcon( image, "Demo", pm );
            try...{
                st.add( ti );
            } catch( AWTException awte ) ...{
                awte.printStackTrace();
            }
        }
    }
    public static void sendMail( String mail ) ...{
        if( desktop != null &&
            desktop.isSupported( Desktop.Action.MAIL ) ) ...{
            try ...{
                desktop.mail( new URI( mail ) );
            } catch (IOException e) ...{
                e.printStackTrace();
            } catch (URISyntaxException e) ...{
                e.printStackTrace();
            }
        }
    }
    public static void openBrowser( String url ) ...{
        if( desktop != null &&
            desktop.isSupported( Desktop.Action.BROWSE )) ...{
            try ...{
                desktop.browse( new URI( url ) );
            } catch (IOException e) ...{
                e.printStackTrace();
            } catch (URISyntaxException e) ...{
                e.printStackTrace();
            }
        }
    }
    public static void edit() ...{
        if( desktop != null &&
            desktop.isSupported( Desktop.Action.EDIT ) ) ...{
            File file = new File( "test.txt" );
            try ...{
                if( file.exists() == false ) ...{
                    file.create();
                }
                desktop.edit( file );
            } catch( IOException ioe ) ...{
                ioe.printStackTrace();
            }
        }
    }
    public static void createPopupMenu() ...{
        pm = new PopupMenu();
        MenuItem ob = new MenuItem( "Open url" );
        ob.addActionListener( new ActionListener() ...{
            public void actionPerformed( ActionEvent ae ) ...{
                openBrowser( "http://blog.csdn.net/xumingming64398966" );
            }
        });
        MenuItem sm = new MenuItem( "Send Mail" );
        sm.addActionListener( new ActionListener() ...{
            public void actionPerformed( ActionEvent ae ) ...{
                sendMail( "[e-mail]" );
            }
        });
        MenuItem ed = new MenuItem( "Edit" );
        ed.addActionListener( new ActionListener() ...{
            public void actionPerformed( ActionEvent ae ) ...{
                edit();
            }
        });
        MenuItem ex = new MenuItem( "Exit" );
        ex.addActionListener( new ActionListener() ...{
            public void actionPerformed( ActionEvent ae ) ...{
                System.exit( 0 );
            }
        });
        pm.add( ob );
        pm.add( sm );
        pm.add( ed );
        pm.addSeparator();
        pm.add( ex );
    }
}



２．Console. JDK6中提供了java.io.Console类专用来访问基于字符的控制台设备. 你的程序如果要与Windows下的cmd或者Linux下的Terminal交互,就可以用Console类代劳. 但我们不总是能得到可用的Console, 一个JVM是否有可用的Console依赖于底层平台和JVM如何被调用. 如果JVM是在交互式命令行(比如Windows的cmd)中启动的,并且输入输出没有重定向到另外的地方,那么就可以得到一个可用的Console实例. 下面代码演示了Console类的用法:


import java.io.Console;

public class ConsoleTest ...{
    public static void main( String[] args ) ...{
        Console console = System.console();
        if( console != null ) ...{
            String user = new String( console.readLine( "Enter User:", new Object[ 0 ] ) );
            String pwd = new String( console.readPassword( "Enter Password:", new Object[ 0 ] ));
            console.printf( "User name is:%s", new Object[]...{user} );
            console.printf( "Password is:%s", new Object[]...{pwd} );
        } else ...{
            System.out.println( "No Console!" );
        }
    }
}


你如果是在一个IDE中如eclipse, netbeans中运行你将得到：
No Console!
因为只有在命令行中才能得到Console对象。

３．Compiler API. 现在我们可以用JDK6 的Compiler API(JSR 199)去动态编译Java源文件，Compiler API结合反射功能就可以实现动态的产生Java代码并编译执行这些代码，有点动态语言的特征。这个特性对于某些需要用到动态编译的应用程序相当有用，比如JSP Web Server，当我们手动修改JSP后，是不希望需要重启Web Server才可以看到效果的，这时候我们就可以用Compiler API来实现动态编译JSP文件，当然，现在的JSP Web Server也是支持JSP热部署的，现在的JSP Web Server通过在运行期间通过Runtime.exec或ProcessBuilder来调用javac来编译代码，这种方式需要我们产生另一个进程去做编译工作，不够优雅而且容易使代码依赖与特定的操作系统；Compiler API通过一套易用的标准的API提供了更加丰富的方式去做动态编译,而且是跨平台的。 下面代码演示了Compiler API的使用：


import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Iterator;

import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;

public class CompilerAPITest ...{
    private final static String srcFileName = "Test.java";
    private final static String classFileName = "Test.class";
    private final static String className = "Test";
   
    public static void main( String[] args ) ...{
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        if( compiler == null ) ...{
            System.err.println( "Compiler is null!" );
            return;
        }
        StandardJavaFileManager fileManager = compiler.getStandardFileManager( null, null, null );
        generateJavaClass();
       
        Iterable < ? extends JavaFileObject> sourceFiles = fileManager.getJavaFileObjects( new String[]...{ srcFileName } );
        compiler.getTask( null, fileManager, null, null, null, sourceFiles ).call();
        try ...{
            fileManager.close();
            Class.forName( className ).newInstance();
        } catch (IOException e) ...{
            e.printStackTrace();
        } catch (InstantiationException e) ...{
            e.printStackTrace();
        } catch (IllegalAccessException e) ...{
            e.printStackTrace();
        } catch (ClassNotFoundException e) ...{
            e.printStackTrace();
        }
    }
   
    public static void generateJavaClass() ...{
        try ...{
            FileWriter rw = new FileWriter( srcFileName );
            BufferedWriter bw = new BufferedWriter( rw );
            bw.write( "public class " + className + " {" );
            bw.newLine();
           
            bw.write( "public " + className + "() {");
            bw.newLine();
            bw.write( "System.out.println( 'you are in the constructor of Class Test' );" );
            bw.write( "}" );
            bw.newLine();
           
            bw.write( "}" );
            bw.flush();
            bw.close();
        } catch (IOException e) ...{
            e.printStackTrace();
        }
    }
}

我在运行这个例子的时候发现ToolProvider.getSystemJavaCompiler得到的是NULL,后来上网一查，原来是一个Bug!链接如下：
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6477844

Closed, not reproducible
那为什么我一直在reproduce阿？

4.Http Server API. JDK6提供了一个简单的Http Server API,据此我们可以构建自己的嵌入式Http Server,它支持Http和Https协议,提供了HTTP1.1的部分实现，没有被实现的那部分可以通过扩展已有的Http Server API来实现,程序员必须自己实现HttpHandler接口,HttpServer会调用HttpHandler实现类的回调方法来处理客户端请求,在这里,我们把一个Http请求和它的响应称为一个交换,包装成HttpExchange类,HttpServer负责将HttpExchange传给 HttpHandler实现类的回调方法.下面代码演示了怎样创建自己的Http Server .



import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetSocketAddress;

import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;

public class HttpServerAPITest ...{
    private static int count = 0;
    public static void main( String[] args ) ...{
        try ...{
            HttpServer hs = HttpServer.create( new InetSocketAddress( 8888 ), 0 );
            hs.createContext( "/", new MyHandler() );
            hs.createContext( "/java", new MyHandler() );
            hs.setExecutor( null );
            hs.start();
            System.out.println( "---begin---" );
            System.out.println( "Listening on " + hs.getAddress() );
        } catch( IOException ioe ) ...{
            ioe.printStackTrace();
        }
    }
    static class MyHandler implements HttpHandler ...{
        public void handle( HttpExchange he ) throws IOException ...{
            System.out.println( "Request " + count++  );
            System.out.println( he.getHttpContext().getPath() );
           
            InputStream is = he.getRequestBody();
            String response = "<font color='blue'>Happy Spring Festerval</font>";
            he.sendResponseHeaders( 200, response.length() );
            OutputStream os = he.getResponseBody();
            os.write( response.getBytes() );
            os.close();
        }
    }
}



效果如图:



5.对脚本语言的支持如: ruby, groovy, javascript.

代码如下:

import java.io.FileReader;

import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

public class ScriptTest ...{
    public static void main( String[] args ) ...{
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName( "ECMAScript" );
        try ...{
            engine.eval( new FileReader( "C:\test.js" ) );
            Invocable invocableEngine = (Invocable)engine;
            Object ret = invocableEngine.invokeFunction( "test", null );
            System.out.println( "The result is :" + (Double)ret );
        } catch( Exception e ) ...{
            e.printStackTrace();
        }
    }
}

test.js如下:

function test()...{
    return Math.round( 11.2 );
}
6.插入式注解处理API(Pluggable Annotation Processing API)，插入式注解处理API(JSR 269)提供一套标准API来处理Annotations.JSR 269用Annotation Processor在编译期间而不是运行期间处理Annotation, Annotation Processor相当于编译器的一个插件,所以称为插入式注解处理.如果Annotation Processor处理Annotation时(执行process方法)产生了新的Java代码,编译器会再调用一次Annotation Processor,如果第二次处理还有新代码产生,就会接着调用Annotation Processor,直到没有新代码产生为止.每执行一次process()方法被称为一个"round",这样整个Annotation processing过程可以看作是一个round的序列.
举个例子：们想建立一套基于Annotation的单元测试框架(如TestNG),在测试类里面用Annotation来标识测试期间需要执行的测试方法,如下所示:


@TestMethod
public void testCheckName()...{
       //do something here
}

这时我们就可以用JSR 269提供的API来处理测试类,根据Annotation提取出需要执行的测试方法.


再举个例子: 下面我用代码演示如何来用JSR 269提供的API来处理Annotations和读取Java源文件的元数据(metadata)


import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.AnnotationMirror;
import javax.lang.model.element.AnnotationValue;
import javax.lang.model.element.Element;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.TypeElement;
import javax.lang.model.util.ElementFilter;
import javax.tools.Diagnostic.Kind;

@SupportedAnnotationTypes( "ToBeTested" )
@SupportedSourceVersion( SourceVersion.RELEASE_6 )
public class MyAnnotationProcessor extends AbstractProcessor ...{
    private void note( String msg ) ...{
        processingEnv.getMessager().printMessage( Kind.NOTE, msg );
    }
    public boolean process( Set< ? extends TypeElement > annotations, RoundEnvironment roundEnv ) ...{
        for( TypeElement te : annotations ) ...{
            note( "annotation: " + te.toString() );
        }
        Set< ? extends Element > elements = roundEnv.getRootElements();
        for( Element e : elements ) ...{
            List< ? extends Element > enclosedElems = e.getEnclosedElements();
            List< ? extends ExecutableElement > ees = ElementFilter.methodsIn( enclosedElems );
            for( ExecutableElement ee : ees ) ...{
                note( "Executable Element Name: " + ee.getSimpleName() );
                List< ? extends AnnotationMirror > as = ee.getAnnotationMirrors();
                note( " as: " + as );
                for( AnnotationMirror am : as )...{
                    Map< ? extends ExecutableElement, ? extends AnnotationValue > map = am.getElementValues();
                    Set< ? extends ExecutableElement > ks = map.keySet();
                    for( ExecutableElement k : ks ) ...{
                        AnnotationValue av = map.get( k );
                        note("----"+ee.getSimpleName()+"."+k.getSimpleName()+"="+av.getValue());
                    }
                }
            }
        }
        return false;
    }
}




public class Testing ...{
    @ToBeTested(group="A")
    public void m1()...{
    }
    @ToBeTested(group="B",owner="QQ")
    public void m2()...{
    }   
}



import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention( RetentionPolicy.RUNTIME )
@Target( ElementType.METHOD )
public @interface ToBeTested ...{
    String owner() default "Chinajash";
    String group();
}

效果如下：


7.SAX. SAX是The Streaming API for XML的缩写，是继DOM(Document Object Model)和SAX(Simple API for XML)之后的又一种处理xml的api,一种利用拉模式解析(pull-parsing)XML文档的API.SAX通过提供一种基于事件迭代器(Iterator)的API让程序员去控制xml文档解析过程,程序遍历这个事件迭代器去处理每一个解析事件，解析事件可以看做是程序拉出来的，也就是程序促使解析器产生一个解析事件然后处理该事件，之后又促使解析器产生下一个解析事件，如此循环直到碰到文档结束符；SAX也是基于事件处理xml文档，但却是用推模式解析，解析器解析完整个xml文档后，才产生解析事件，然后推给程序去处理这些事件；DOM采用的方式是将整个xml文档映射到一颗内存树，这样就可以很容易地得到父节点和子结点以及兄弟节点的数据，但如果文档很大，将会严重影响性能。

下面是个例子：



import java.io.FileNotFoundException;
import java.io.FileOutputStream;

import javax.xml.namespace.QName;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamWriter;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;

public class SaxTest ...{
    public static void main( String[] arg ) throws XMLStreamException, FileNotFoundException ...{
        readXMLBySAX();
        writeXMLBySAX();
    }
    public static void readXMLBySAX() throws XMLStreamException, FileNotFoundException ...{
        XMLInputFactory factory = XMLInputFactory.newInstance();
        XMLEventReader  reader = factory.createXMLEventReader( SaxTest.class.getResourceAsStream( "test.xml" ) );
        XMLEvent event;
        StringBuffer  parsingResult = new StringBuffer();
        while( reader.hasNext() ) ...{
            event = reader.nextEvent();
            if( event.isStartElement() ) ...{
                StartElement se = event.asStartElement();
                parsingResult.append( "<" );
                parsingResult.append( se.getName() );
                if( se.getName().getLocalPart().equals( "catalog" ) ) ...{
                    parsingResult.append( "id="" );
                    parsingResult.append( se.getAttributeByName( new QName( "id" ) ).getValue());
                    parsingResult.append( """ ) ;
                }
                parsingResult.append( ">" );
            } else if( event.isCharacters() ) ...{
                parsingResult.append( event.asCharacters().getData() );
            } else if( event.isEndElement() ) ...{
                parsingResult.append( "</" );
                parsingResult.append( event.asEndElement().getName() );
                parsingResult.append( ">" );
            }
        }
        System.out.println( parsingResult );
    }
   
    public static void writeXMLBySAX() throws XMLStreamException, FileNotFoundException ...{
        XMLOutputFactory factory = XMLOutputFactory.newInstance();
        XMLStreamWriter writer = factory.createXMLStreamWriter( new FileOutputStream( "output.xml" ) );
        writer.writeStartDocument();
        writer.writeCharacters( " " );
        writer.writeComment( "testing comment" );
        writer.writeCharacters( " " );
        writer.writeStartElement( "catalogs" );
        writer.writeNamespace( "myNS", "http://blog.csdn.net/Chinajash" );
        writer.writeAttribute( "owner", "sina" );
        writer.writeCharacters( " " );
        writer.writeStartElement("http://blog.csdn.net/Chinajash", "catalog");
        writer.writeAttribute("id","007");
        writer.writeCharacters("Apparel");
        // 写入catalog元素的结束标签
        writer.writeEndElement();
        // 写入catalogs元素的结束标签
        writer.writeEndElement();
        // 结束 XML 文档
        writer.writeEndDocument();        
        writer.close();

    }
}

test.xml:



<?xml version="1.0" encoding="UTF-8"?>
<catalogs>
    <catalog id="001">Book</catalog>
    <catalog id="002">Video</catalog>
</catalogs>


8. Web Service. 由于Web服务日趋流行，利用Web服务的功能性的API特征正从最新的Java EE版本中向Java SE 6平台迁移。换言之，针对Web服务不需另外加入额外的工具，在Java EE和Java SE平台拥有相同的API。野马将大把不同的Web服务相关的API加到标准的工具柜中：以JSR 181针对Java 平台的Web服务元数据，通过JSR 224的基于XML 的Web服务Java API（JAX-WS）；针对Java的带有附件的SOAP API（SAAJ）作为JSR 67 。与三个Web服务API相关的包新增到Java SE 6.0里：JAX－WS API 放置到javax.xml.ws包； SAAJ类在javax.xml.soap 包； Web服务的元数据类放置在javax.jws包里。 下面是一个简单的例子，　下面的代码是要作为web service发布的类。


package hello;
import javax.jws.WebService;
import javax.xml.ws.Endpoint;

@WebService
public class CircleFunctions ...{
    public double getArea( int radius ) ...{
        return Math.PI * radius * radius;
    }
    public double getCircumference( int radius ) ...{
        return Math.PI * radius * 2;
    }
   
    public static void main( String[] args ) ...{
        Endpoint.publish( "http://localhost:8888/WebServiceExample/circlefunctions", new CircleFunctions());
    }
}



处理的方法如下：
javac -d ./ CircleFunctions.java
wsgen hello.CircleFunctions
java hello.CircleFunctions
然后在浏览器中输入如下url,你将得到一个xml页面：
http: //localhost:8888/WebServiceExample/circlefunctions?WSDL

参考网页：
1.Desktop和SystemTray. http://dev.yesky.com/411/3019911.shtml
2.Console. http://dev.yesky.com/133/3032133.shtml
3.Compiler API. http://developer.51cto.com/art/200701/37359.htm
4.HttpServer API. http://www.testage.net/QA/Dev/200701/1396.htm
5. 对脚本语言的支持http://blog.edwardro.com/read.php?167
6. 插入式注解处理API. http://ourconan.com.cn/article.php?itemid-2113-type-blog.html
7.SAX. http://ourconan.com.cn/article.php?itemid-2111-type-blog.html
8.Web Service. http://www.360doc.com/showWeb/0/0/298124.aspx
9.JDK1.5的Annotation