精简jre（1）

1、copy jre到jar同文件夹，编写批处理文件make.bat

 

@echo off
set path=%cd%/jre/bin
java -jar -verbose:class my.jar >>class.txt
pause

 

2、执行此bat文件会把my.jar运行时用到的类写到class.txt文件中

 

下面就是处理class.txt文件

 

public void ff(String filePath, String contain) {File file = new File(filePath);File file2 = new File("D:/result.txt");BufferedReader reader = null;BufferedWriter writer = null;try {reader = new BufferedReader(new FileReader(file));writer = new BufferedWriter(new FileWriter(file2));String tempString = null;while ((tempString = reader.readLine()) != null) {if (tempString.contains(contain)) {writer.write(tempString + "/n");}}reader.close();} catch (IOException e) {e.printStackTrace();} finally {if (reader != null) {try {reader.close();} catch (IOException e) {e.printStackTrace();}}if(writer != null){try {writer.close();} catch (IOException e) {e.printStackTrace();}}}} 

 

此方法是要保留class.txt文件中含有rt.jar字符串的行

例如 ：               Main.ff("D:/class.txt", "rt.jar");

 

 

3、经过第二步，得到result.txt文件

 

此时里面的内容形如：

 

[Loaded java.lang.RuntimeException from C:/Documents and Settings/root/桌面/test/jre/lib/rt.jar]

 

然后就是利用文本编辑器Ctrl + H 替换无用内容为空格

最后形成这样的格式 java/lang/RuntimeException

 

4、下面要做的就是将jre里rt.jar文件解压缩到rt文件夹，然后执行下面的程序

 

import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStreamReader;import java.io.LineNumberReader;public class ReduceRt {// 文件拷贝public static boolean copy(String file1, String file2) {try // must try and catch,otherwide will compile error{// instance the File as file_in and file_outjava.io.File file_in = new java.io.File(file1);java.io.File file_out = new java.io.File(file2);FileInputStream in1 = new FileInputStream(file_in);FileOutputStream out1 = new FileOutputStream(file_out);byte[] bytes = new byte[1024];int c;while ((c = in1.read(bytes)) != -1)out1.write(bytes, 0, c);in1.close();out1.close();return (true); // if success then return true}catch (Exception e) {System.out.println("Error!");return (false); // if fail then return false}}// 读取路径,copypublic static int dealClass(String needfile, String sdir, String odir)throws IOException {int sn = 0; // 成功个数File usedclass = new File(needfile);if (usedclass.canRead()) {String line = null;LineNumberReader reader = new LineNumberReader(new InputStreamReader(new FileInputStream(usedclass),"UTF-8"));while ((line = reader.readLine()) != null) {line = line.trim();int dirpos = line.lastIndexOf("/");if (dirpos > 0) {String dir = odir + line.substring(0, dirpos);File fdir = new File(dir);if (!fdir.exists())fdir.mkdirs();String sf = sdir + line + ".class";String of = odir + line + ".class";boolean copy_ok = copy(sf.trim(), of.trim());if (copy_ok)sn++;else {System.out.println(line);}}}}return sn;}public static void main(String[] args) {String needfile = "D:/result.txt";String sdir = "D:/rt/";String odir = "D:/rt1/";try {int sn = dealClass(needfile, sdir, odir);System.out.print(sn);} catch (IOException e) {// TODO 自动生成 catch 块e.printStackTrace();}}} 

执行完，可以将使用到类copy到rt1文件夹中，打包rt1文件夹为rt.zip 重名为为rt.jar

 

替换原来的rt.jar

 

 

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