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Commonly used programming tasks in java
package com.venky.reflection;
import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.objectweb.asm.AnnotationVisitor;
import org.objectweb.asm.Attribute;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.MethodVisitor;
public class Reflector {
protected final Class reflectedClass;
protected final Class upperBoundClass;
protected final List allMethods ;
protected final List> classHierarchy ;
protected final List> classForest ;
protected Reflector(Class reflectedClass,Class upperBoundClass){
assert(upperBoundClass != null);
assert(reflectedClass != null);
assert(upperBoundClass.isAssignableFrom(reflectedClass));
this.reflectedClass = reflectedClass ;
this.upperBoundClass = upperBoundClass;
this.allMethods = new ArrayList(reflectedClass.getMethods().length);
this.classHierarchy = new ArrayList>();
this.classForest = new ArrayList>();
Class rClass = reflectedClass;
List> interfaces = new ArrayList>();
do {
loadMethods(rClass);
classHierarchy.add(rClass);
classForest.add(rClass);
Class parentClass = getParentClass(rClass,upperBoundClass);
for (Class i : rClass.getInterfaces()){
if (i == parentClass){
continue;
}
interfaces.clear(); //Instead of new ArrayList each time.
loadAllInterfaces(i, interfaces);
for (Class c : interfaces){
loadMethods(c);
}
classForest.addAll(interfaces);
}
rClass = parentClass;
}while(rClass != null );
}
private void loadMethods(Class clazz){
int index = 0;
if (clazz == upperBoundClass){
index = allMethods.size();
}
for(Method m:getDeclaredMethods(clazz)){
List methodsForSignature = getMethodsForSignature(getMethodSignature(m));
if (methodsForSignature.isEmpty()){
allMethods.add(index,m);
index++;
}
methodsForSignature.add(m);
}
}
public List> getClassHierarchy(){
return classHierarchy;
}
public List> getClassForest(){
return classForest;
}
public boolean isAnnotationPresent(Class annotationClass){
boolean present = false;
for (Class clazz:getClassForest()){
present = clazz.isAnnotationPresent(annotationClass);
if (present){
break;
}
}
return present;
}
public T getAnnotation(Class annotationClass){
T annotation = null;
for (Class clazz:getClassForest()){
annotation = clazz.getAnnotation(annotationClass);
if (annotation != null){
break;
}
}
return annotation;
}
public boolean isAnnotationPresent(Method method, Class annotationClass){
if (method.isAnnotationPresent(annotationClass)){
return true;
}
boolean present = false;
List methods = getMethodsForSignature(getMethodSignature(method));
for (int i = 0 ; !present && i < methods.size() ; i ++){
Method m = methods.get(i);
present = m.isAnnotationPresent(annotationClass);
}
return present;
}
public T getAnnotation(Method method,Class annotationClass){
if (method.isAnnotationPresent(annotationClass)){
return method.getAnnotation(annotationClass);
}
T annotation = null;
List methods = getMethodsForSignature(getMethodSignature(method));
for (int i = 0 ; annotation == null && i < methods.size() ; i ++){
Method m = methods.get(i);
annotation = m.getAnnotation(annotationClass);
}
return annotation;
}
private Map methodSignature = new HashMap();
protected String getMethodSignature(Method method){
String ret = methodSignature.get(method);
if (ret != null){
return ret;
}
int modifiers = method.getModifiers();
StringBuilder sign = new StringBuilder();
sign.append(Modifier.isPublic(modifiers) ? "public " : Modifier.isProtected(modifiers) ? "protected " : Modifier.isPrivate(modifiers)? "private " : "");
sign.append(method.getReturnType().toString() + " ");
sign.append(method.getName() + "(");
Class[] pt = method.getParameterTypes();
for (int i = 0 ; i< pt.length ; i++ ){
if (i > 0){
sign.append(",");
}
sign.append(pt[i]);
}
sign.append(")");
ret = sign.toString();
methodSignature.put(method, ret);
return ret;
}
private Map> methodsWithSameSignature = new HashMap>();
protected List getMethodsForSignature(String signature){
List methods = methodsWithSameSignature.get(signature);
if (methods == null){
methods = new ArrayList();
methodsWithSameSignature.put(signature, methods);
}
return methods;
}
protected List getDeclaredMethods(Class forClass){
List methods = new ArrayList();
methods.addAll(Arrays.asList(forClass.getDeclaredMethods()));
try {
ClassReader reader = new ClassReader(getClass().getClassLoader().getResourceAsStream(forClass.getName().replace('.', '/')+ ".class"));
ClassVisitorImpl mv = new ClassVisitorImpl();
reader.accept(mv, 0);
final Map mSeq = mv.getMethodSequenceMap();
Collections.sort(methods,new Comparator(){
public int compare(Method o1, Method o2) {
return mSeq.get(o1.getName()).compareTo(mSeq.get(o2.getName()));
}
});
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
return methods;
}
public Class getParentClass(){
return getParentClass(reflectedClass);
}
public Class getParentClass(Class clazz){
int i = classHierarchy.indexOf(clazz);
if (i >= 0 && i < classHierarchy.size() - 1){
return classHierarchy.get(i+1);
}
return null;
}
private static class ClassVisitorImpl implements ClassVisitor {
private Map methodSequenceMap = new HashMap();
public Map getMethodSequenceMap() {
return methodSequenceMap;
}
public void visit(int version, int access, String name,
String signature, String superName, String[] interfaces) {
}
public void visitSource(String source, String debug) {
}
public void visitOuterClass(String owner, String name, String desc) {
}
public AnnotationVisitor visitAnnotation(String desc, boolean visible) {
return null;
}
public void visitAttribute(Attribute attr) {
}
public void visitInnerClass(String name, String outerName,
String innerName, int access) {
}
public FieldVisitor visitField(int access, String name, String desc,
String signature, Object value) {
return null;
}
public MethodVisitor visitMethod(int access, String name, String desc,
String signature, String[] exceptions) {
methodSequenceMap.put(name,methodSequenceMap.size());
return null;
}
public void visitEnd() {
}
}
public final List getMethods(MethodMatcher matcher){
List methods = new ArrayList();
for (Method method:allMethods){
if (matcher.matches(method)){
methods.add(method);
}
}
return methods;
}
public static interface MethodMatcher {
public boolean matches(Method method);
}
private static void loadAllInterfaces(Class clazz,List> interfaces){
if (clazz.isInterface()){
interfaces.add(clazz);
}
for (Class infcClass: clazz.getInterfaces()){
loadAllInterfaces(infcClass, interfaces);
}
}
public static Class getParentClass(Class clazz,Class aSuperInfcOrClass){
Class c = clazz;
if (aSuperInfcOrClass != null && !aSuperInfcOrClass.isAssignableFrom(c)){
throw new RuntimeException(c.getName() + " is not a "+ aSuperInfcOrClass.getName());
}
if (c.isInterface()){
List> interfaces = new ArrayList>();
for (Class infc: c.getInterfaces()){
if (aSuperInfcOrClass == null || aSuperInfcOrClass.isAssignableFrom(infc)){
interfaces.add(infc);
}
if (interfaces.size() > 1){
break;
}
}
if (interfaces.isEmpty()){
return null;
}else if (interfaces.size() > 1){
throw new RuntimeException ("multiple interfaces implement " + aSuperInfcOrClass.getName());
}else {
return interfaces.get(0);
}
}else {
c = c.getSuperclass();
if (c != null && (aSuperInfcOrClass == null || aSuperInfcOrClass.isAssignableFrom(c))){
return c;
}else {
return null;
}
}
}
}