public ProxyingInstantiator(Class<T> type) {
byte[] classBytes = writeExtendingClass(type, SUFFIX);
try {
newType =
ClassDefinitionUtils.defineClass(
type.getName() + SUFFIX, classBytes, type.getClassLoader());
} catch (Exception e) {
throw new ObjenesisException(e);
}
}
@SuppressWarnings("unchecked")
public T newInstance() {
try {
return (T) newType.newInstance();
} catch (InstantiationException e) {
throw new ObjenesisException(e);
} catch (IllegalAccessException e) {
throw new ObjenesisException(e);
}
}
/**
* Will generate the bytes for a class extending the type passed in parameter. This class will
* only have an empty default constructor
*
* @param type type to extend
* @param suffix the suffix appended to the class name to create the next extending class name
* @return the byte for the class
* @throws ObjenesisException is something goes wrong
*/
private static byte[] writeExtendingClass(Class<?> type, String suffix) {
String parentClazz = classNameToInternalClassName(type.getName());
String clazz = parentClazz + suffix;
DataOutputStream in = null;
ByteArrayOutputStream bIn =
new ByteArrayOutputStream(1000); // 1000 should be large enough to fit the entire class
try {
in = new DataOutputStream(bIn);
in.write(MAGIC);
in.write(VERSION);
in.writeShort(CONSTANT_POOL_COUNT);
// set all the constant pool here
// 1. class
in.writeByte(CONSTANT_Class);
in.writeShort(INDEX_UTF8_CLASS);
// 2. super class
in.writeByte(CONSTANT_Class);
in.writeShort(INDEX_UTF8_SUPERCLASS);
// 3. default constructor name
in.writeByte(CONSTANT_Utf8);
in.writeUTF(CONSTRUCTOR_NAME);
// 4. default constructor description
in.writeByte(CONSTANT_Utf8);
in.writeUTF(CONSTRUCTOR_DESC);
// 5. Code
in.writeByte(CONSTANT_Utf8);
in.writeUTF("Code");
// 6. Class name
in.writeByte(CONSTANT_Utf8);
in.writeUTF("L" + clazz + ";");
// 7. Class name (again)
in.writeByte(CONSTANT_Utf8);
in.writeUTF(clazz);
// 8. Superclass name
in.writeByte(CONSTANT_Utf8);
in.writeUTF(parentClazz);
// end of constant pool
// access flags: We want public, ACC_SUPER is always there
in.writeShort(ACC_PUBLIC | ACC_SUPER);
// this class index in the constant pool
in.writeShort(INDEX_CLASS_THIS);
// super class index in the constant pool
in.writeShort(INDEX_CLASS_SUPERCLASS);
// interfaces implemented count (we have none)
in.writeShort(0);
// fields count (we have none)
in.writeShort(0);
// methods count (we have one: the default constructor)
in.writeShort(1);
// default constructor method_info
in.writeShort(ACC_PUBLIC);
in.writeShort(INDEX_UTF8_CONSTRUCTOR_NAME); // index of the method name (<init>)
in.writeShort(INDEX_UTF8_CONSTRUCTOR_DESC); // index of the description
in.writeShort(1); // number of attributes: only one, the code
// code attribute of the default constructor
in.writeShort(INDEX_UTF8_CODE_ATTRIBUTE);
in.writeInt(CODE_ATTRIBUTE_LENGTH); // attribute length
in.writeShort(1); // max_stack
in.writeShort(1); // max_locals
in.writeInt(CODE.length); // code length
in.write(CODE);
in.writeShort(0); // exception_table_length = 0
in.writeShort(
0); // attributes count = 0, no need to have LineNumberTable and LocalVariableTable
// class attributes
in.writeShort(0); // none. No need to have a source file attribute
} catch (IOException e) {
throw new ObjenesisException(e);
} finally {
if (in != null) {
try {
in.close();
} catch (IOException e) {
throw new ObjenesisException(e);
}
}
}
return bIn.toByteArray();
}
