org.activiti.engine.impl.javax.el.BeanELResolver Maven / Gradle / Ivy
/*
* Based on JUEL 2.2.1 code, 2006-2009 Odysseus Software GmbH
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.activiti.engine.impl.javax.el;
import java.beans.FeatureDescriptor;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Array;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* Defines property resolution behavior on objects using the JavaBeans component architecture. This
* resolver handles base objects of any type, as long as the base is not null. It accepts any object
* as a property, and coerces it to a string. That string is then used to find a JavaBeans compliant
* property on the base object. The value is accessed using JavaBeans getters and setters. This
* resolver can be constructed in read-only mode, which means that isReadOnly will always return
* true and {@link #setValue(ELContext, Object, Object, Object)} will always throw
* PropertyNotWritableException. ELResolvers are combined together using {@link CompositeELResolver}
* s, to define rich semantics for evaluating an expression. See the javadocs for {@link ELResolver}
* for details. Because this resolver handles base objects of any type, it should be placed near the
* end of a composite resolver. Otherwise, it will claim to have resolved a property before any
* resolvers that come after it get a chance to test if they can do so as well.
*
* @see CompositeELResolver
* @see ELResolver
*/
public class BeanELResolver extends ELResolver {
protected static final class BeanProperties {
private final Map map = new HashMap();
public BeanProperties(Class baseClass) {
PropertyDescriptor[] descriptors;
try {
descriptors = Introspector.getBeanInfo(baseClass).getPropertyDescriptors();
} catch (IntrospectionException e) {
throw new ELException(e);
}
for (PropertyDescriptor descriptor : descriptors) {
map.put(descriptor.getName(), new BeanProperty(descriptor));
}
}
public BeanProperty getBeanProperty(String property) {
return map.get(property);
}
}
protected static final class BeanProperty {
private final PropertyDescriptor descriptor;
public BeanProperty(PropertyDescriptor descriptor) {
this.descriptor = descriptor;
}
public Class getPropertyType() {
return descriptor.getPropertyType();
}
public Method getReadMethod() {
return findAccessibleMethod(descriptor.getReadMethod());
}
public Method getWriteMethod() {
return findAccessibleMethod(descriptor.getWriteMethod());
}
public boolean isReadOnly() {
return findAccessibleMethod(descriptor.getWriteMethod()) == null;
}
}
private static Method findAccessibleMethod(Method method) {
if (method == null || method.isAccessible()) {
return method;
}
try {
method.setAccessible(true);
} catch (SecurityException e) {
for (Class cls : method.getDeclaringClass().getInterfaces()) {
Method mth = null;
try {
mth = cls.getMethod(method.getName(), method.getParameterTypes());
mth = findAccessibleMethod(mth);
if (mth != null) {
return mth;
}
} catch (NoSuchMethodException ignore) {
// do nothing
}
}
Class cls = method.getDeclaringClass().getSuperclass();
if (cls != null) {
Method mth = null;
try {
mth = cls.getMethod(method.getName(), method.getParameterTypes());
mth = findAccessibleMethod(mth);
if (mth != null) {
return mth;
}
} catch (NoSuchMethodException ignore) {
// do nothing
}
}
return null;
}
return method;
}
private final boolean readOnly;
private final ConcurrentHashMap, BeanProperties> cache;
private ExpressionFactory defaultFactory;
/**
* Creates a new read/write BeanELResolver.
*/
public BeanELResolver() {
this(false);
}
/**
* Creates a new BeanELResolver whose read-only status is determined by the given parameter.
*/
public BeanELResolver(boolean readOnly) {
this.readOnly = readOnly;
this.cache = new ConcurrentHashMap, BeanProperties>();
}
/**
* If the base object is not null, returns the most general type that this resolver accepts for
* the property argument. Otherwise, returns null. Assuming the base is not null, this method
* will always return Object.class. This is because any object is accepted as a key and is
* coerced into a string.
*
* @param context
* The context of this evaluation.
* @param base
* The bean to analyze.
* @return null if base is null; otherwise Object.class.
*/
@Override
public Class getCommonPropertyType(ELContext context, Object base) {
return isResolvable(base) ? Object.class : null;
}
/**
* If the base object is not null, returns an Iterator containing the set of JavaBeans
* properties available on the given object. Otherwise, returns null. The Iterator returned must
* contain zero or more instances of java.beans.FeatureDescriptor. Each info object contains
* information about a property in the bean, as obtained by calling the
* BeanInfo.getPropertyDescriptors method. The FeatureDescriptor is initialized using the same
* fields as are present in the PropertyDescriptor, with the additional required named
* attributes "type" and "resolvableAtDesignTime" set as follows:
*
* - {@link ELResolver#TYPE} - The runtime type of the property, from
* PropertyDescriptor.getPropertyType().
* - {@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} - true.
*
*
* @param context
* The context of this evaluation.
* @param base
* The bean to analyze.
* @return An Iterator containing zero or more FeatureDescriptor objects, each representing a
* property on this bean, or null if the base object is null.
*/
@Override
public Iterator getFeatureDescriptors(ELContext context, Object base) {
if (isResolvable(base)) {
final PropertyDescriptor[] properties;
try {
properties = Introspector.getBeanInfo(base.getClass()).getPropertyDescriptors();
} catch (IntrospectionException e) {
return Collections. emptyList().iterator();
}
return new Iterator() {
int next = 0;
public boolean hasNext() {
return properties != null && next < properties.length;
}
public FeatureDescriptor next() {
PropertyDescriptor property = properties[next++];
FeatureDescriptor feature = new FeatureDescriptor();
feature.setDisplayName(property.getDisplayName());
feature.setName(property.getName());
feature.setShortDescription(property.getShortDescription());
feature.setExpert(property.isExpert());
feature.setHidden(property.isHidden());
feature.setPreferred(property.isPreferred());
feature.setValue(TYPE, property.getPropertyType());
feature.setValue(RESOLVABLE_AT_DESIGN_TIME, true);
return feature;
}
public void remove() {
throw new UnsupportedOperationException("cannot remove");
}
};
}
return null;
}
/**
* If the base object is not null, returns the most general acceptable type that can be set on
* this bean property. If the base is not null, the propertyResolved property of the ELContext
* object must be set to true by this resolver, before returning. If this property is not true
* after this method is called, the caller should ignore the return value. The provided property
* will first be coerced to a String. If there is a BeanInfoProperty for this property and there
* were no errors retrieving it, the propertyType of the propertyDescriptor is returned.
* Otherwise, a PropertyNotFoundException is thrown.
*
* @param context
* The context of this evaluation.
* @param base
* The bean to analyze.
* @param property
* The name of the property to analyze. Will be coerced to a String.
* @return If the propertyResolved property of ELContext was set to true, then the most general
* acceptable type; otherwise undefined.
* @throws NullPointerException
* if context is null
* @throws PropertyNotFoundException
* if base is not null and the specified property does not exist or is not readable.
* @throws ELException
* if an exception was thrown while performing the property or variable resolution.
* The thrown exception must be included as the cause property of this exception, if
* available.
*/
@Override
public Class getType(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
Class result = null;
if (isResolvable(base)) {
result = toBeanProperty(base, property).getPropertyType();
context.setPropertyResolved(true);
}
return result;
}
/**
* If the base object is not null, returns the current value of the given property on this bean.
* If the base is not null, the propertyResolved property of the ELContext object must be set to
* true by this resolver, before returning. If this property is not true after this method is
* called, the caller should ignore the return value. The provided property name will first be
* coerced to a String. If the property is a readable property of the base object, as per the
* JavaBeans specification, then return the result of the getter call. If the getter throws an
* exception, it is propagated to the caller. If the property is not found or is not readable, a
* PropertyNotFoundException is thrown.
*
* @param context
* The context of this evaluation.
* @param base
* The bean to analyze.
* @param property
* The name of the property to analyze. Will be coerced to a String.
* @return If the propertyResolved property of ELContext was set to true, then the value of the
* given property. Otherwise, undefined.
* @throws NullPointerException
* if context is null
* @throws PropertyNotFoundException
* if base is not null and the specified property does not exist or is not readable.
* @throws ELException
* if an exception was thrown while performing the property or variable resolution.
* The thrown exception must be included as the cause property of this exception, if
* available.
*/
@Override
public Object getValue(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
Object result = null;
if (isResolvable(base)) {
Method method = toBeanProperty(base, property).getReadMethod();
if (method == null) {
throw new PropertyNotFoundException("Cannot read property " + property);
}
try {
result = method.invoke(base);
} catch (InvocationTargetException e) {
// for an invocation target exception, the causing exception is not the Cause()
// but the target exception
throw new ELException(e.getTargetException());
} catch (Exception e) {
throw new ELException(e);
}
context.setPropertyResolved(true);
}
return result;
}
/**
* If the base object is not null, returns whether a call to
* {@link #setValue(ELContext, Object, Object, Object)} will always fail. If the base is not
* null, the propertyResolved property of the ELContext object must be set to true by this
* resolver, before returning. If this property is not true after this method is called, the
* caller can safely assume no value was set.
*
* @param context
* The context of this evaluation.
* @param base
* The bean to analyze.
* @param property
* The name of the property to analyze. Will be coerced to a String.
* @return If the propertyResolved property of ELContext was set to true, then true if calling
* the setValue method will always fail or false if it is possible that such a call may
* succeed; otherwise undefined.
* @throws NullPointerException
* if context is null
* @throws PropertyNotFoundException
* if base is not null and the specified property does not exist or is not readable.
* @throws ELException
* if an exception was thrown while performing the property or variable resolution.
* The thrown exception must be included as the cause property of this exception, if
* available.
*/
@Override
public boolean isReadOnly(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
boolean result = readOnly;
if (isResolvable(base)) {
result |= toBeanProperty(base, property).isReadOnly();
context.setPropertyResolved(true);
}
return result;
}
/**
* If the base object is not null, attempts to set the value of the given property on this bean.
* If the base is not null, the propertyResolved property of the ELContext object must be set to
* true by this resolver, before returning. If this property is not true after this method is
* called, the caller can safely assume no value was set. If this resolver was constructed in
* read-only mode, this method will always throw PropertyNotWritableException. The provided
* property name will first be coerced to a String. If property is a writable property of base
* (as per the JavaBeans Specification), the setter method is called (passing value). If the
* property exists but does not have a setter, then a PropertyNotFoundException is thrown. If
* the property does not exist, a PropertyNotFoundException is thrown.
*
* @param context
* The context of this evaluation.
* @param base
* The bean to analyze.
* @param property
* The name of the property to analyze. Will be coerced to a String.
* @param value
* The value to be associated with the specified key.
* @throws NullPointerException
* if context is null
* @throws PropertyNotFoundException
* if base is not null and the specified property does not exist or is not readable.
* @throws PropertyNotWritableException
* if this resolver was constructed in read-only mode, or if there is no setter for
* the property
* @throws ELException
* if an exception was thrown while performing the property or variable resolution.
* The thrown exception must be included as the cause property of this exception, if
* available.
*/
@Override
public void setValue(ELContext context, Object base, Object property, Object value) {
if (context == null) {
throw new NullPointerException();
}
if (isResolvable(base)) {
if (readOnly) {
throw new PropertyNotWritableException("resolver is read-only");
}
Method method = toBeanProperty(base, property).getWriteMethod();
if (method == null) {
throw new PropertyNotWritableException("Cannot write property: " + property);
}
try {
method.invoke(base, value);
} catch (InvocationTargetException e) {
// for an invocation target exception, the causing exception is not the Cause()
// but the target exception
throw new ELException("Cannot write property: " + property, e.getTargetException());
} catch (IllegalAccessException e) {
throw new PropertyNotWritableException("Cannot write property: " + property, e);
}
context.setPropertyResolved(true);
}
}
/**
* If the base object is not null, invoke the method, with the given parameters on
* this bean. The return value from the method is returned.
*
*
* If the base is not null, the propertyResolved property of the
* ELContext object must be set to true by this resolver, before
* returning. If this property is not true after this method is called, the caller
* should ignore the return value.
*
*
*
* The provided method object will first be coerced to a String. The methods in the
* bean is then examined and an attempt will be made to select one for invocation. If no
* suitable can be found, a MethodNotFoundException is thrown.
*
* If the given paramTypes is not null, select the method with the given name and
* parameter types.
*
* Else select the method with the given name that has the same number of parameters. If there
* are more than one such method, the method selection process is undefined.
*
* Else select the method with the given name that takes a variable number of arguments.
*
* Note the resolution for overloaded methods will likely be clarified in a future version of
* the spec.
*
* The provided parameters are coerced to the corresponding parameter types of the method, and
* the method is then invoked.
*
* @param context
* The context of this evaluation.
* @param base
* The bean on which to invoke the method
* @param method
* The simple name of the method to invoke. Will be coerced to a String.
* If method is "<init>"or "<clinit>" a MethodNotFoundException is
* thrown.
* @param paramTypes
* An array of Class objects identifying the method's formal parameter types, in
* declared order. Use an empty array if the method has no parameters. Can be
* null, in which case the method's formal parameter types are assumed
* to be unknown.
* @param params
* The parameters to pass to the method, or null if no parameters.
* @return The result of the method invocation (null if the method has a
* void return type).
* @throws MethodNotFoundException
* if no suitable method can be found.
* @throws ELException
* if an exception was thrown while performing (base, method) resolution. The thrown
* exception must be included as the cause property of this exception, if available.
* If the exception thrown is an InvocationTargetException, extract its
* cause and pass it to the ELException constructor.
* @since 2.2
*/
@Override
public Object invoke(ELContext context, Object base, Object method, Class[] paramTypes, Object[] params) {
if (context == null) {
throw new NullPointerException();
}
Object result = null;
if (isResolvable(base)) {
if (params == null) {
params = new Object[0];
}
String name = method.toString();
Method target = findMethod(base, name, paramTypes, params.length);
if (target == null) {
throw new MethodNotFoundException("Cannot find method " + name + " with " + params.length + " parameters in " + base.getClass());
}
try {
result = target.invoke(base, coerceParams(getExpressionFactory(context), target, params));
} catch (InvocationTargetException e) {
// for an invocation target exception, the causing exception is not the Cause()
// but the target exception
throw new ELException(e.getTargetException());
} catch (IllegalAccessException e) {
throw new ELException(e);
}
context.setPropertyResolved(true);
}
return result;
}
private Method findMethod(Object base, String name, Class[] types, int paramCount) {
if (types != null) {
try {
return findAccessibleMethod(base.getClass().getMethod(name, types));
} catch (NoSuchMethodException e) {
return null;
}
}
Method varArgsMethod = null;
for (Method method : base.getClass().getMethods()) {
if (method.getName().equals(name)) {
int formalParamCount = method.getParameterTypes().length;
if (method.isVarArgs() && paramCount >= formalParamCount - 1) {
varArgsMethod = method;
} else if (paramCount == formalParamCount) {
return findAccessibleMethod(method);
}
}
}
return varArgsMethod == null ? null : findAccessibleMethod(varArgsMethod);
}
/**
* Lookup an expression factory used to coerce method parameters in context under key
* "javax.el.ExpressionFactory".
* If no expression factory can be found under that key, use a default instance created with
* {@link ExpressionFactory#newInstance()}.
* @param context
* The context of this evaluation.
* @return expression factory instance
*/
private ExpressionFactory getExpressionFactory(ELContext context) {
Object obj = context.getContext(ExpressionFactory.class);
if (obj instanceof ExpressionFactory) {
return (ExpressionFactory)obj;
}
if (defaultFactory == null) {
defaultFactory = ExpressionFactory.newInstance();
}
return defaultFactory;
}
private Object[] coerceParams(ExpressionFactory factory, Method method, Object[] params) {
Class[] types = method.getParameterTypes();
Object[] args = new Object[types.length];
if (method.isVarArgs()) {
int varargIndex = types.length - 1;
if (params.length < varargIndex) {
throw new ELException("Bad argument count");
}
for (int i = 0; i < varargIndex; i++) {
coerceValue(args, i, factory, params[i], types[i]);
}
Class varargType = types[varargIndex].getComponentType();
int length = params.length - varargIndex;
Object array = null;
if (length == 1) {
Object source = params[varargIndex];
if (source != null && source.getClass().isArray()) {
if (types[varargIndex].isInstance(source)) { // use source array as is
array = source;
} else { // coerce array elements
length = Array.getLength(source);
array = Array.newInstance(varargType, length);
for (int i = 0; i < length; i++) {
coerceValue(array, i, factory, Array.get(source, i), varargType);
}
}
} else { // single element array
array = Array.newInstance(varargType, 1);
coerceValue(array, 0, factory, source, varargType);
}
} else {
array = Array.newInstance(varargType, length);
for (int i = 0; i < length; i++) {
coerceValue(array, i, factory, params[varargIndex + i], varargType);
}
}
args[varargIndex] = array;
} else {
if (params.length != args.length) {
throw new ELException("Bad argument count");
}
for (int i = 0; i < args.length; i++) {
coerceValue(args, i, factory, params[i], types[i]);
}
}
return args;
}
private void coerceValue(Object array, int index, ExpressionFactory factory, Object value, Class type) {
if (value != null || type.isPrimitive()) {
Array.set(array, index, factory.coerceToType(value, type));
}
}
/**
* Test whether the given base should be resolved by this ELResolver.
*
* @param base
* The bean to analyze.
* @param property
* The name of the property to analyze. Will be coerced to a String.
* @return base != null
*/
private final boolean isResolvable(Object base) {
return base != null;
}
/**
* Lookup BeanProperty for the given (base, property) pair.
*
* @param base
* The bean to analyze.
* @param property
* The name of the property to analyze. Will be coerced to a String.
* @return The BeanProperty representing (base, property).
* @throws PropertyNotFoundException
* if no BeanProperty can be found.
*/
private final BeanProperty toBeanProperty(Object base, Object property) {
BeanProperties beanProperties = cache.get(base.getClass());
if (beanProperties == null) {
BeanProperties newBeanProperties = new BeanProperties(base.getClass());
beanProperties = cache.putIfAbsent(base.getClass(), newBeanProperties);
if (beanProperties == null) { // put succeeded, use new value
beanProperties = newBeanProperties;
}
}
BeanProperty beanProperty = property == null ? null : beanProperties.getBeanProperty(property.toString());
if (beanProperty == null) {
throw new PropertyNotFoundException("Could not find property " + property + " in " + base.getClass());
}
return beanProperty;
}
/**
* This method is not part of the API, though it can be used (reflectively) by clients of this
* class to remove entries from the cache when the beans are being unloaded.
*
* Note: this method is present in the reference implementation, so we're adding it here to ease
* migration.
*
* @param classloader
* The classLoader used to load the beans.
*/
@SuppressWarnings("unused")
private final void purgeBeanClasses(ClassLoader loader) {
Iterator> classes = cache.keySet().iterator();
while (classes.hasNext()) {
if (loader == classes.next().getClassLoader()) {
classes.remove();
}
}
}
}