从Jar文件中的Class文件读取字节 [英] Read bytes from a Class file within a Jar file
本文介绍了从Jar文件中的Class文件读取字节的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有一个.jar
文件,其中有.class
个文件和.java
个文件.我想将特定的.class
文件的内容作为byte[]
数组加载.
I have a .jar
file which has .class
files and .java
files. I want to load the contents of a specific .class
file as a byte[]
array.
static byte[] getBytes(String javaFileName, String jar) throws IOException {
try (JarFile jarFile = new JarFile(jar)) {
Enumeration<JarEntry> entries = jarFile.entries();
while (entries.hasMoreElements()) {
JarEntry entry = entries.nextElement();
// We are only interested in .class files spawned by compiling the argument file.
if (entry.getName().endsWith(".class") &&
entry.getName().contains(Files.getNameWithoutExtension(javaFileName))) {
try (InputStream inputStream = jarFile.getInputStream(entry)) {
return Preconditions.checkNotNull(ByteStreams.toByteArray(inputStream));
} catch (IOException ioException) {
System.out.println("Could not obtain class entry for " + entry.getName());
throw ioException;
}
}
}
}
}
但是,当我运行此代码时,将向我返回一个空字节数组(new byte[0]
).关于我可能在这里做错的任何想法吗?
However, when I run this code, an empty byte array (new byte[0]
) is returned to me. Any ideas on what I may be doing wrong here?
该代码可以正常工作!错误是问题的另一部分.无论如何,为了知识起见,把问题放在这里:)
This code works just fine! The error was in another part of the question. Keeping the question here for knowledge's sake anyway :)
推荐答案
这对我有用:
public class Main {
public static void main(String[] args) {
try {
byte[] bytes = getBytes("MeasurePrinter.class", "~/BundleSensorAlarmLib.jar");
System.out.println(bytesToHex(bytes));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private static byte[] getBytes(String javaFileName, String jar) throws IOException {
// ... inputs check omitted ...
try (JarFile jarFile = new JarFile(jar)) {
Enumeration<JarEntry> entries = jarFile.entries();
while (entries.hasMoreElements()) {
JarEntry entry = entries.nextElement();
// We are only interested in .class files spawned by compiling the argument file.
if (entry.getName().endsWith(".class") &&
entry.getName().contains(javaFileName.substring(0, javaFileName.lastIndexOf(".")))) {
try (InputStream inputStream = jarFile.getInputStream(entry)) {
return getBytes(inputStream);
} catch (IOException ioException) {
System.out.println("Could not obtain class entry for " + entry.getName());
throw ioException;
}
}
}
}
throw new IOException("File not found");
}
private static byte[] getBytes(InputStream is) throws IOException {
try (ByteArrayOutputStream os = new ByteArrayOutputStream();)
{
byte[] buffer = new byte[0xFFFF];
for (int len; (len = is.read(buffer)) != -1;)
os.write(buffer, 0, len);
os.flush();
return os.toByteArray();
}
}
private static char[] hexArray = "0123456789ABCDEF".toCharArray();
public static String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for ( int j = 0; j < bytes.length; j++ ) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
}
从返回的字节数组不为空的意义上说.
in the sense that the returned byte array is not empty.
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