1 概述

本文主要講述了如何利用xsel在Linux環(huán)境下對系統(tǒng)剪貼板的訪問。

2 起因

在搜索引擎直接搜索“Java訪問剪貼板”，大部分都是直接使用AWT API進行訪問的例子：

Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard(); StringSelection selection = new StringSelection("test"); clipboard.setContents(selection, selection);

但是，一個最大的問題是，需要該程序一直運行，才能訪問到剪貼板，因此，如果沒有其他處理邏輯，需要加上線程休眠代碼：

Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard(); StringSelection selection = new StringSelection("test"); clipboard.setContents(selection, selection); TimeUnit.HOURS.sleep(1);

換句話說，這樣只是臨時復(fù)制到剪貼板，并沒有永久復(fù)制，那么，有沒有其他辦法可以在運行程序結(jié)束之后也能訪問到剪貼板呢？

3 xsel

xsel是Linux下訪問剪貼板的命令行工具，類似的還有xclip，沒有安裝的可以使用包管理器安裝。其中寫入到剪貼板命令如下：

echo "test clipboard" | xsel -ib

由此想到了可以嘗試使用Runtime：

public static void main(String[] args) throws Exception {Runtime runtime = Runtime.getRuntime();// 直接執(zhí)行命令Process process = runtime.exec("echo \"111\" | xsel -ib");// 等待執(zhí)行結(jié)束process.waitFor();StringBuilder builder = new StringBuilder();// 獲取輸出BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));for (String s; ((s = reader.readLine()) != null); ) {builder.append(s);}System.out.println(builder);builder = new StringBuilder();// 獲取錯誤輸出reader = new BufferedReader(new InputStreamReader(process.getErrorStream()));for (String s; ((s = reader.readLine()) != null); ) {builder.append(s);}System.out.println(builder);// 獲取返回值int exitValue = process.exitValue();System.out.println("exitValue is " + exitValue);if (exitValue != 0) {System.out.println("error");}process.destroy(); }

運行之后輸出如下：

"111" | xsel -ib "111" | xsel -ib exitValue is 0

可以看到輸出結(jié)果是不正常的，這樣就相當(dāng)于變成了執(zhí)行

echo "\"111\" | xsel -ib"

也就是輸出的字符串都是echo的參數(shù)。

4 創(chuàng)建腳本文件

出現(xiàn)上面結(jié)果的原因是Process并不能直接支持使用管道運算符，因此，采用直接創(chuàng)建腳本運行命令的方法。

步驟：

• 創(chuàng)建臨時腳本文件：使用Files.createFile創(chuàng)建
• 授權(quán)：700權(quán)限，也就是所有者讀、寫、執(zhí)行權(quán)限，使用Files.setPosixFilePermissions
• 寫入腳本文件：向腳本文件寫入echo str | xsel -ib，使用Files.writeString
• 執(zhí)行：利用Process.exec執(zhí)行腳本文件
• 刪除：利用Files.delete刪除臨時文件

代碼如下：

public static void main(String[] args) throws Exception {String fileName = "1.sh";Path executeFile = Files.createFile(Path.of(fileName));Files.setPosixFilePermissions(executeFile, Set.of(PosixFilePermission.OWNER_WRITE,PosixFilePermission.OWNER_EXECUTE, PosixFilePermission.OWNER_READ));String clipboardContent = "111";Files.writeString(executeFile, "echo " + clipboardContent + " | xsel -ib");Runtime runtime = Runtime.getRuntime();Process process = runtime.exec("./" + fileName);process.waitFor();StringBuilder builder = new StringBuilder();BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));for (String s; ((s = reader.readLine()) != null); ) {builder.append(s);}System.out.println(builder);builder = new StringBuilder();reader = new BufferedReader(new InputStreamReader(process.getErrorStream()));for (String s; ((s = reader.readLine()) != null); ) {builder.append(s);}System.out.println(builder);int exitValue = process.exitValue();System.out.println("exitValue is " + exitValue);if (exitValue != 0) {System.out.println("error");}Files.delete(executeFile);process.destroy(); }

輸出：

exitValue is 0

有兩行空行是System.out.println()的換行輸出，說明Process的inputStream以及errorStream都沒有內(nèi)容。

測試結(jié)果也是正常，能夠剪貼出111字符串。

5 從剪貼板讀取

從剪貼板讀取的原理類似，就是xsel的參數(shù)不一樣，這里不展開了，放上完整代碼：

import java.io.BufferedReader; import java.io.InputStreamReader; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.attribute.PosixFilePermission; import java.util.Set;public class Main {private static final String FILENAME = "1.sh";public static void main(String[] args) throws Exception {writeToClipboard("111111");System.out.println(readFromClipboard());writeToClipboard("22222");System.out.println(readFromClipboard());}//寫入到剪貼板private static void writeToClipboard(String content) throws Exception {Path executeFile = createFile("echo " + content + " | xsel -ib");exec(executeFile);}//從剪貼板讀取private static String readFromClipboard() throws Exception {Path executeFile = createFile("xsel -ob");return exec(executeFile);}private static Path createFile(String fileContent) throws Exception {Path executeFile = Files.createFile(Path.of(FILENAME));Files.setPosixFilePermissions(executeFile, Set.of(PosixFilePermission.OWNER_WRITE,PosixFilePermission.OWNER_EXECUTE, PosixFilePermission.OWNER_READ));Files.writeString(executeFile, fileContent);return executeFile;}private static String exec(Path executeFile) throws Exception {Runtime runtime = Runtime.getRuntime();Process process = runtime.exec("./" + FILENAME);process.waitFor();StringBuilder builder = new StringBuilder();BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));for (String s; ((s = reader.readLine()) != null); ) {builder.append(s);}String res = "";if (builder.length() != 0) {res = builder.toString();}reader = new BufferedReader(new InputStreamReader(process.getErrorStream()));builder = new StringBuilder();for (String s; ((s = reader.readLine()) != null); ) {builder.append(s);}if (builder.length() != 0) {System.out.println(builder);}int exitValue = process.exitValue();System.out.println("exitValue is " + exitValue);if (exitValue != 0) {System.out.println("error");}Files.delete(executeFile);process.destroy();return res;} }

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