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General data-binding functionality for Jackson: works on core streaming API
package com.fasterxml.jackson.databind.util;
import java.lang.reflect.*;
import java.util.*;
import com.fasterxml.jackson.databind.annotation.JacksonStdImpl;
public final class ClassUtil
{
/*
/**********************************************************
/* Methods that deal with inheritance
/**********************************************************
*/
/**
* Method that will find all sub-classes and implemented interfaces
* of a given class or interface. Classes are listed in order of
* precedence, starting with the immediate super-class, followed by
* interfaces class directly declares to implemented, and then recursively
* followed by parent of super-class and so forth.
* Note that Object.class is not included in the list
* regardless of whether endBefore argument is defined or not.
*
* @param endBefore Super-type to NOT include in results, if any; when
* encountered, will be ignored (and no super types are checked).
*/
public static List> findSuperTypes(Class cls, Class endBefore) {
return findSuperTypes(cls, endBefore, new ArrayList>(8));
}
public static List> findSuperTypes(Class cls, Class endBefore, List> result) {
_addSuperTypes(cls, endBefore, result, false);
return result;
}
private static void _addSuperTypes(Class cls, Class endBefore, Collection> result, boolean addClassItself) {
if (cls == endBefore || cls == null || cls == Object.class) { return; }
if (addClassItself) {
if (result.contains(cls)) { // already added, no need to check supers
return;
}
result.add(cls);
}
for (Class intCls : cls.getInterfaces()) {
_addSuperTypes(intCls, endBefore, result, true);
}
_addSuperTypes(cls.getSuperclass(), endBefore, result, true);
}
/*
/**********************************************************
/* Class type detection methods
/**********************************************************
*/
/**
* @return Null if class might be a bean; type String (that identifies
* why it's not a bean) if not
*/
public static String canBeABeanType(Class type)
{
// First: language constructs that ain't beans:
if (type.isAnnotation()) {
return "annotation";
}
if (type.isArray()) {
return "array";
}
if (type.isEnum()) {
return "enum";
}
if (type.isPrimitive()) {
return "primitive";
}
// Anything else? Seems valid, then
return null;
}
public static String isLocalType(Class type, boolean allowNonStatic)
{
/* As per [JACKSON-187], GAE seems to throw SecurityExceptions
* here and there... and GAE itself has a bug, too
* (see []). Bah. So we need to catch some wayward exceptions on GAE
*/
try {
// one more: method locals, anonymous, are not good:
if (type.getEnclosingMethod() != null) {
return "local/anonymous";
}
/* But how about non-static inner classes? Can't construct
* easily (theoretically, we could try to check if parent
* happens to be enclosing... but that gets convoluted)
*/
if (!allowNonStatic) {
if (type.getEnclosingClass() != null) {
if (!Modifier.isStatic(type.getModifiers())) {
return "non-static member class";
}
}
}
}
catch (SecurityException e) { }
catch (NullPointerException e) { }
return null;
}
/**
* Method for finding enclosing class for non-static inner classes
*/
public static Class getOuterClass(Class type)
{
// as above, GAE has some issues...
try {
// one more: method locals, anonymous, are not good:
if (type.getEnclosingMethod() != null) {
return null;
}
if (!Modifier.isStatic(type.getModifiers())) {
return type.getEnclosingClass();
}
} catch (SecurityException e) { }
catch (NullPointerException e) { }
return null;
}
/**
* Helper method used to weed out dynamic Proxy types; types that do
* not expose concrete method API that we could use to figure out
* automatic Bean (property) based serialization.
*/
public static boolean isProxyType(Class type)
{
// As per [Issue#57], should NOT disqualify JDK proxy:
/*
// Then: well-known proxy (etc) classes
if (Proxy.isProxyClass(type)) {
return true;
}
*/
String name = type.getName();
// Hibernate uses proxies heavily as well:
if (name.startsWith("net.sf.cglib.proxy.")
|| name.startsWith("org.hibernate.proxy.")) {
return true;
}
// Not one of known proxies, nope:
return false;
}
/**
* Helper method that checks if given class is a concrete one;
* that is, not an interface or abstract class.
*/
public static boolean isConcrete(Class type)
{
int mod = type.getModifiers();
return (mod & (Modifier.INTERFACE | Modifier.ABSTRACT)) == 0;
}
public static boolean isConcrete(Member member)
{
int mod = member.getModifiers();
return (mod & (Modifier.INTERFACE | Modifier.ABSTRACT)) == 0;
}
public static boolean isCollectionMapOrArray(Class type)
{
if (type.isArray()) return true;
if (Collection.class.isAssignableFrom(type)) return true;
if (Map.class.isAssignableFrom(type)) return true;
return false;
}
/*
/**********************************************************
/* Type name handling methods
/**********************************************************
*/
/**
* Helper method used to construct appropriate description
* when passed either type (Class) or an instance; in latter
* case, class of instance is to be used.
*/
public static String getClassDescription(Object classOrInstance)
{
if (classOrInstance == null) {
return "unknown";
}
Class cls = (classOrInstance instanceof Class) ?
(Class) classOrInstance : classOrInstance.getClass();
return cls.getName();
}
/*
/**********************************************************
/* Class loading
/**********************************************************
*/
public static Class findClass(String className) throws ClassNotFoundException
{
// [JACKSON-597]: support primitive types (and void)
if (className.indexOf('.') < 0) {
if ("int".equals(className)) return Integer.TYPE;
if ("long".equals(className)) return Long.TYPE;
if ("float".equals(className)) return Float.TYPE;
if ("double".equals(className)) return Double.TYPE;
if ("boolean".equals(className)) return Boolean.TYPE;
if ("byte".equals(className)) return Byte.TYPE;
if ("char".equals(className)) return Character.TYPE;
if ("short".equals(className)) return Short.TYPE;
if ("void".equals(className)) return Void.TYPE;
}
// Two-phase lookup: first using context ClassLoader; then default
Throwable prob = null;
ClassLoader loader = Thread.currentThread().getContextClassLoader();
if (loader != null) {
try {
return Class.forName(className, true, loader);
} catch (Exception e) {
prob = getRootCause(e);
}
}
try {
return Class.forName(className);
} catch (Exception e) {
if (prob == null) {
prob = getRootCause(e);
}
}
if (prob instanceof RuntimeException) {
throw (RuntimeException) prob;
}
throw new ClassNotFoundException(prob.getMessage(), prob);
}
/*
/**********************************************************
/* Method type detection methods
/**********************************************************
*/
public static boolean hasGetterSignature(Method m)
{
// First: static methods can't be getters
if (Modifier.isStatic(m.getModifiers())) {
return false;
}
// Must take no args
Class[] pts = m.getParameterTypes();
if (pts != null && pts.length != 0) {
return false;
}
// Can't be a void method
if (Void.TYPE == m.getReturnType()) {
return false;
}
// Otherwise looks ok:
return true;
}
/*
/**********************************************************
/* Exception handling
/**********************************************************
*/
/**
* Method that can be used to find the "root cause", innermost
* of chained (wrapped) exceptions.
*/
public static Throwable getRootCause(Throwable t)
{
while (t.getCause() != null) {
t = t.getCause();
}
return t;
}
/**
* Method that will unwrap root causes of given Throwable, and throw
* the innermost {@link Exception} or {@link Error} as is.
* This is useful in cases where mandatory wrapping is added, which
* is often done by Reflection API.
*/
public static void throwRootCause(Throwable t) throws Exception
{
t = getRootCause(t);
if (t instanceof Exception) {
throw (Exception) t;
}
throw (Error) t;
}
/**
* Method that will wrap 't' as an {@link IllegalArgumentException} if it
* is a checked exception; otherwise (runtime exception or error) throw as is
*/
public static void throwAsIAE(Throwable t)
{
throwAsIAE(t, t.getMessage());
}
/**
* Method that will wrap 't' as an {@link IllegalArgumentException} (and with
* specified message) if it
* is a checked exception; otherwise (runtime exception or error) throw as is
*/
public static void throwAsIAE(Throwable t, String msg)
{
if (t instanceof RuntimeException) {
throw (RuntimeException) t;
}
if (t instanceof Error) {
throw (Error) t;
}
throw new IllegalArgumentException(msg, t);
}
/**
* Method that will locate the innermost exception for given Throwable;
* and then wrap it as an {@link IllegalArgumentException} if it
* is a checked exception; otherwise (runtime exception or error) throw as is
*/
public static void unwrapAndThrowAsIAE(Throwable t)
{
throwAsIAE(getRootCause(t));
}
/**
* Method that will locate the innermost exception for given Throwable;
* and then wrap it as an {@link IllegalArgumentException} if it
* is a checked exception; otherwise (runtime exception or error) throw as is
*/
public static void unwrapAndThrowAsIAE(Throwable t, String msg)
{
throwAsIAE(getRootCause(t), msg);
}
/*
/**********************************************************
/* Instantiation
/**********************************************************
*/
/**
* Method that can be called to try to create an instantiate of
* specified type. Instantiation is done using default no-argument
* constructor.
*
* @param canFixAccess Whether it is possible to try to change access
* rights of the default constructor (in case it is not publicly
* accessible) or not.
*
* @throws IllegalArgumentException If instantiation fails for any reason;
* except for cases where constructor throws an unchecked exception
* (which will be passed as is)
*/
public static T createInstance(Class cls, boolean canFixAccess)
throws IllegalArgumentException
{
Constructor ctor = findConstructor(cls, canFixAccess);
if (ctor == null) {
throw new IllegalArgumentException("Class "+cls.getName()+" has no default (no arg) constructor");
}
try {
return ctor.newInstance();
} catch (Exception e) {
ClassUtil.unwrapAndThrowAsIAE(e, "Failed to instantiate class "+cls.getName()+", problem: "+e.getMessage());
return null;
}
}
public static Constructor findConstructor(Class cls, boolean canFixAccess)
throws IllegalArgumentException
{
try {
Constructor ctor = cls.getDeclaredConstructor();
if (canFixAccess) {
checkAndFixAccess(ctor);
} else {
// Has to be public...
if (!Modifier.isPublic(ctor.getModifiers())) {
throw new IllegalArgumentException("Default constructor for "+cls.getName()+" is not accessible (non-public?): not allowed to try modify access via Reflection: can not instantiate type");
}
}
return ctor;
} catch (NoSuchMethodException e) {
;
} catch (Exception e) {
ClassUtil.unwrapAndThrowAsIAE(e, "Failed to find default constructor of class "+cls.getName()+", problem: "+e.getMessage());
}
return null;
}
/*
/**********************************************************
/* Primitive type support
/**********************************************************
*/
/**
* Helper method used to get default value for wrappers used for primitive types
* (0 for Integer etc)
*/
public static Object defaultValue(Class cls)
{
if (cls == Integer.TYPE) {
return Integer.valueOf(0);
}
if (cls == Long.TYPE) {
return Long.valueOf(0L);
}
if (cls == Boolean.TYPE) {
return Boolean.FALSE;
}
if (cls == Double.TYPE) {
return Double.valueOf(0.0);
}
if (cls == Float.TYPE) {
return Float.valueOf(0.0f);
}
if (cls == Byte.TYPE) {
return Byte.valueOf((byte) 0);
}
if (cls == Short.TYPE) {
return Short.valueOf((short) 0);
}
if (cls == Character.TYPE) {
return '\0';
}
throw new IllegalArgumentException("Class "+cls.getName()+" is not a primitive type");
}
/**
* Helper method for finding wrapper type for given primitive type (why isn't
* there one in JDK?)
*/
public static Class wrapperType(Class primitiveType)
{
if (primitiveType == Integer.TYPE) {
return Integer.class;
}
if (primitiveType == Long.TYPE) {
return Long.class;
}
if (primitiveType == Boolean.TYPE) {
return Boolean.class;
}
if (primitiveType == Double.TYPE) {
return Double.class;
}
if (primitiveType == Float.TYPE) {
return Float.class;
}
if (primitiveType == Byte.TYPE) {
return Byte.class;
}
if (primitiveType == Short.TYPE) {
return Short.class;
}
if (primitiveType == Character.TYPE) {
return Character.class;
}
throw new IllegalArgumentException("Class "+primitiveType.getName()+" is not a primitive type");
}
/*
/**********************************************************
/* Access checking/handling methods
/**********************************************************
*/
/**
* Method called to check if we can use the passed method or constructor
* (wrt access restriction -- public methods can be called, others
* usually not); and if not, if there is a work-around for
* the problem.
*/
public static void checkAndFixAccess(Member member)
{
// We know all members are also accessible objects...
AccessibleObject ao = (AccessibleObject) member;
/* 14-Jan-2009, tatu: It seems safe and potentially beneficial to
* always to make it accessible (latter because it will force
* skipping checks we have no use for...), so let's always call it.
*/
//if (!ao.isAccessible()) {
try {
ao.setAccessible(true);
} catch (SecurityException se) {
/* 17-Apr-2009, tatu: Related to [JACKSON-101]: this can fail on
* platforms like EJB and Google App Engine); so let's
* only fail if we really needed it...
*/
if (!ao.isAccessible()) {
Class declClass = member.getDeclaringClass();
throw new IllegalArgumentException("Can not access "+member+" (from class "+declClass.getName()+"; failed to set access: "+se.getMessage());
}
}
//}
}
/*
/**********************************************************
/* Enum type detection
/**********************************************************
*/
/**
* Helper method that can be used to dynamically figure out
* enumeration type of given {@link EnumSet}, without having
* access to its declaration.
* Code is needed to work around design flaw in JDK.
*/
public static Class> findEnumType(EnumSet s)
{
// First things first: if not empty, easy to determine
if (!s.isEmpty()) {
return findEnumType(s.iterator().next());
}
// Otherwise need to locate using an internal field
return EnumTypeLocator.instance.enumTypeFor(s);
}
/**
* Helper method that can be used to dynamically figure out
* enumeration type of given {@link EnumSet}, without having
* access to its declaration.
* Code is needed to work around design flaw in JDK.
*/
public static Class> findEnumType(EnumMap m)
{
if (!m.isEmpty()) {
return findEnumType(m.keySet().iterator().next());
}
// Otherwise need to locate using an internal field
return EnumTypeLocator.instance.enumTypeFor(m);
}
/**
* Helper method that can be used to dynamically figure out formal
* enumeration type (class) for given enumeration. This is either
* class of enum instance (for "simple" enumerations), or its
* superclass (for enums with instance fields or methods)
*/
@SuppressWarnings("unchecked")
public static Class> findEnumType(Enum en)
{
// enums with "body" are sub-classes of the formal type
Class ec = en.getClass();
if (ec.getSuperclass() != Enum.class) {
ec = ec.getSuperclass();
}
return (Class>) ec;
}
/**
* Helper method that can be used to dynamically figure out formal
* enumeration type (class) for given class of an enumeration value.
* This is either class of enum instance (for "simple" enumerations),
* or its superclass (for enums with instance fields or methods)
*/
@SuppressWarnings("unchecked")
public static Class> findEnumType(Class cls)
{
// enums with "body" are sub-classes of the formal type
if (cls.getSuperclass() != Enum.class) {
cls = cls.getSuperclass();
}
return (Class>) cls;
}
/*
/**********************************************************
/* Jackson-specific stuff
/**********************************************************
*/
/**
* Method that can be called to determine if given Object is the default
* implementation Jackson uses; as opposed to a custom serializer installed by
* a module or calling application. Determination is done using
* {@link JacksonStdImpl} annotation on handler (serializer, deserializer etc)
* class.
*/
public static boolean isJacksonStdImpl(Object impl) {
return (impl != null) && isJacksonStdImpl(impl.getClass());
}
public static boolean isJacksonStdImpl(Class implClass) {
return (implClass.getAnnotation(JacksonStdImpl.class) != null);
}
public static boolean isBogusClass(Class cls) {
return (cls == Void.class || cls == Void.TYPE
|| cls == com.fasterxml.jackson.databind.annotation.NoClass.class);
}
public static boolean isNonStaticInnerClass(Class cls) {
return (cls.getEnclosingClass() != null)
&& !Modifier.isStatic(cls.getModifiers());
}
/*
/**********************************************************
/* Helper classes
/**********************************************************
*/
/**
* Inner class used to contain gory details of how we can determine
* details of instances of common JDK types like {@link EnumMap}s.
*/
private static class EnumTypeLocator
{
final static EnumTypeLocator instance = new EnumTypeLocator();
private final Field enumSetTypeField;
private final Field enumMapTypeField;
private EnumTypeLocator() {
/* JDK uses following fields to store information about actual Enumeration
* type for EnumSets, EnumMaps...
*/
enumSetTypeField = locateField(EnumSet.class, "elementType", Class.class);
enumMapTypeField = locateField(EnumMap.class, "elementType", Class.class);
}
@SuppressWarnings("unchecked")
public Class> enumTypeFor(EnumSet set)
{
if (enumSetTypeField != null) {
return (Class>) get(set, enumSetTypeField);
}
throw new IllegalStateException("Can not figure out type for EnumSet (odd JDK platform?)");
}
@SuppressWarnings("unchecked")
public Class> enumTypeFor(EnumMap set)
{
if (enumMapTypeField != null) {
return (Class>) get(set, enumMapTypeField);
}
throw new IllegalStateException("Can not figure out type for EnumMap (odd JDK platform?)");
}
private Object get(Object bean, Field field)
{
try {
return field.get(bean);
} catch (Exception e) {
throw new IllegalArgumentException(e);
}
}
private static Field locateField(Class fromClass, String expectedName, Class type)
{
Field found = null;
// First: let's see if we can find exact match:
Field[] fields = fromClass.getDeclaredFields();
for (Field f : fields) {
if (expectedName.equals(f.getName()) && f.getType() == type) {
found = f;
break;
}
}
// And if not, if there is just one field with the type, that field
if (found == null) {
for (Field f : fields) {
if (f.getType() == type) {
// If more than one, can't choose
if (found != null) return null;
found = f;
}
}
}
if (found != null) { // it's non-public, need to force accessible
try {
found.setAccessible(true);
} catch (Throwable t) { }
}
return found;
}
}
}