关于Java：如何读取.class文件的全限定名称

How to read the fully qualified name of a .class file

嘿，我想标题总结了一下，但还是这样。

我需要从其编译的.class文件中提取对象的完全限定名称，有人可以指出正确的方向吗？

谢谢，
亚当。

1	getClass().getName()

更新：您可以将类文件加载到byte[]中(使用标准i / o)，然后使用getClass().getClassLoader().defineClass(...)

相关讨论

您可以通过解析二进制文件来阅读。类文件格式在VM Spec中定义。

如果您不了解二进制文件，请看一下DataInputStream。

您可以看一下JSF Implementation中的AnnotationScanner，它们确实手动加载类(以避免烫发空间污染)以查找JSF注释。特别要看一下：

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/**
* This class is encapsulating binary .class file information as defined at
* http://java.sun.com/docs/books/vmspec/2nd-edition/html/ClassFile.doc.html
* <p/>
* This is used by the annotation frameworks to quickly scan .class files
* for the presence of annotations. This avoid the annotation framework
* having to load each .class file in the class loader.
* <p/>
* Taken from the GlassFish V2 source base.
*/
@SuppressWarnings({"UnusedDeclaration"})
private static final class ClassFile {

private static final int magic = 0xCAFEBABE;

public static final int ACC_PUBLIC = 0x1;
public static final int ACC_PRIVATE = 0x2;
public static final int ACC_PROTECTED = 0x4;
public static final int ACC_STATIC = 0x8;
public static final int ACC_FINAL = 0x10;
public static final int ACC_SYNCHRONIZED = 0x20;
public static final int ACC_THREADSAFE = 0x40;
public static final int ACC_TRANSIENT = 0x80;
public static final int ACC_NATIVE = 0x100;
public static final int ACC_INTERFACE = 0x200;
public static final int ACC_ABSTRACT = 0x400;

public short majorVersion;
public short minorVersion;
public ConstantPoolInfo constantPool[];
public short accessFlags;
public ConstantPoolInfo thisClass;
public ConstantPoolInfo superClass;
public ConstantPoolInfo interfaces[];

/**
* bunch of stuff I really don't care too much for now.
* <p/>
* FieldInfo fields[]; MethodInfo methods[];
* AttributeInfo attributes[];
*/

ByteBuffer header;
ConstantPoolInfo constantPoolInfo = new ConstantPoolInfo();

// ------------------------------------------------------------ Constructors

/**
* Creates a new instance of ClassFile
*/
public ClassFile() {
header = ByteBuffer.allocate(12000);
}

// ---------------------------------------------------------- Public Methods

public void setConstantPoolInfo(ConstantPoolInfo poolInfo) {
constantPoolInfo = poolInfo;
}

/**
* Read the input channel and initialize instance data structure.
*
* @param in a <wyn>ReadableByteChannel</wyn> that provides the bytes
* of the classfile
*
* @return <wyn>true</wyn> if the bytes representing this classfile include
* one of the annotations we're looking for.
*
* @throws IOException if an I/O error occurs while reading the class
*/
public boolean containsAnnotation(ReadableByteChannel in)
throws IOException {

/**
* this is the .class file layout
*
ClassFile {
u4 magic;
u2 minor_version;
u2 major_version;
u2 constant_pool_count;
cp_info constant_pool[constant_pool_count-1];
u2 access_flags;
u2 this_class;
u2 super_class;
u2 interfaces_count;
u2 interfaces[interfaces_count];
u2 fields_count;
field_info fields[fields_count];
u2 methods_count;
method_info methods[methods_count];
u2 attributes_count;
attribute_info attributes[attributes_count];
}
**/
header.clear();
long read = (long) in.read(header);
if (read == -1) {
return false;
}
header.rewind();

if (header.getInt() != magic) {
return false;
}

minorVersion = header.getShort();
majorVersion = header.getShort();
int constantPoolSize = header.getShort();

return constantPoolInfo
.containsAnnotation(constantPoolSize, header, in);

}

} // END ClassFile

根据您使用的IDE，可能会有执行此操作的机制。例如，在eclipse中，您可以向下钻取.class文件并右键单击它，然后选择"复制完全限定名称"。

较早版本的eclipse可能没有此功能，但是我之前使用过此插件：

http://www.jave.de/eclipse/copyfully/index.html

它的工作方式几乎相同。希望这可以帮助。