粘贴板操作(Crtl+C/V)

粘贴板操作是很有用的,比如你需要粘贴一段文字，不想要他的格式只想要他的文字或者格式和文字都想要，你复制一个图片信息粘贴导致本地的时候想保存为一个文件，系统是怎么实现的呢。

真相

系统的粘贴功能其实有一个规范的规范编号为：rfc2045
英文名：Multipurpose Internet Mail Extensions (MIME) Part One:Format of Internet Message Bodies
中文翻译：多用途多格式邮件扩展-信体格式说明书
链接：http://www.ietf.org/rfc/rfc2045.txt

这个规范主要描述了网络数据协议格式.格式为：

     entity-headers := [ content CRLF ]
                       [ encoding CRLF ]
                       [ id CRLF ]
                       [ description CRLF ]
                       *( MIME-extension-field CRLF )

     MIME-message-headers := entity-headers
                             fields
                             version CRLF
                             ; The ordering of the header
                             ; fields implied by this BNF
                             ; definition should be ignored.

     MIME-part-headers := entity-headers
                          [ fields ]
                          ; Any field not beginning with
                          ; "content-" can have no defined
                          ; meaning and may be ignored.
                          ; The ordering of the header
                          ; fields implied by this BNF
                          ; definition should be ignored.
#其中 Content-type: 
#image/x-java-image
#Content-type: text/plain; charset=us-ascii 
#...等格式类型

好了以上是一般操作系统粘贴使用的粘贴板协议概述。
详细可以参照rfc2045

Java中的粘贴板

java 中使用awt实现rfc2045 协议，
java.awt.datatransfer.Transferable
java.awt.datatransfer.DataFlavor
java.awt.datatransfer.Clipboard
这三个类实现RFC2045协议

具体Demo代码

package com.ghw.test;

import java.awt.*;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.InputStreamReader;
import java.util.List;

/**
 * Created by cocky on 2017/3/1.
 */
public class TestPaste {
    public String getClipboardText(Clipboard clip) throws Exception {
        Transferable clipT = clip.getContents(null);
        if (clipT != null) {
            if (clipT.isDataFlavorSupported(DataFlavor.stringFlavor))
                return (String) clipT.getTransferData(DataFlavor.stringFlavor);

        }
        return null;
    }
    public BufferedImage getClipboardImage(Clipboard clip) throws Exception {
        Transferable clipT = clip.getContents(null);
        if (clipT != null) {
            if (clipT.isDataFlavorSupported(DataFlavor.imageFlavor))
                return (BufferedImage) clipT.getTransferData(DataFlavor.imageFlavor);
            else {
                System.out.println("Not support");
            }

        }
        return null;
    }


    public InputStreamReader getClipboardplainInputStream(Clipboard clip) throws Exception {
        Transferable clipT = clip.getContents(null);
        if (clipT != null) {
            //自动识别最好的Flavor
            if (clipT.isDataFlavorSupported(DataFlavor.getTextPlainUnicodeFlavor()))
                return (InputStreamReader)clipT.getTransferData(DataFlavor.selectBestTextFlavor(clipT.getTransferDataFlavors()));
            else {
                System.out.println("Not support");
            }

        }
        return null;
    }

    public java.util.List<File> getClipboardFile(Clipboard clip) throws Exception {
        Transferable clipT = clip.getContents(null);
        if (clipT != null) {
            //自动识别最好的Flavor
            if (clipT.isDataFlavorSupported(DataFlavor.javaFileListFlavor))
                return (java.util.List<File>)clipT.getTransferData(DataFlavor.javaFileListFlavor);
            else {
                System.out.println("Not support");
            }

        }
        return null;
    }

    public static void main(String[] args) throws Exception {
        TestPaste testpaste = new TestPaste();
        Clipboard systemClipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
        //直接就是文本，也可以支持把html转为text
        System.out.println("===:"+testpaste.getClipboardText(systemClipboard));
        //图片
        System.out.println("===:"+testpaste.getClipboardImage(systemClipboard));

        //二进制流
        //InputStreamReader paste = testparse.getClipboardplainInputStream(systemClipboard);
        //System.out.println(IOUtils.toString(paste));
        List<File> clipboardFile = testpaste.getClipboardFile(systemClipboard);
        System.out.println(clipboardFile);

    }
}