org.activiti.engine.impl.javax.el
类 BeanELResolver

java.lang.Object
  继承者 org.activiti.engine.impl.javax.el.ELResolver
      继承者 org.activiti.engine.impl.javax.el.BeanELResolver

public class BeanELResolver
extends ELResolver

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 setValue(ELContext, Object, Object, Object) will always throw PropertyNotWritableException. ELResolvers are combined together using CompositeELResolver s, to define rich semantics for evaluating an expression. See the javadocs for 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.

另请参见:
CompositeELResolver, ELResolver

嵌套类摘要
protected static class BeanELResolver.BeanProperties
           
protected static class BeanELResolver.BeanProperty
           
 
字段摘要
 
从类 org.activiti.engine.impl.javax.el.ELResolver 继承的字段
RESOLVABLE_AT_DESIGN_TIME, TYPE
 
构造方法摘要
BeanELResolver()
          Creates a new read/write BeanELResolver.
BeanELResolver(boolean readOnly)
          Creates a new BeanELResolver whose read-only status is determined by the given parameter.
 
方法摘要
 Class<?> getCommonPropertyType(ELContext context, Object base)
          If the base object is not null, returns the most general type that this resolver accepts for the property argument.
 Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base)
          If the base object is not null, returns an Iterator containing the set of JavaBeans properties available on the given object.
 Class<?> getType(ELContext context, Object base, Object property)
          If the base object is not null, returns the most general acceptable type that can be set on this bean property.
 Object getValue(ELContext context, Object base, Object property)
          If the base object is not null, returns the current value of the given property on this bean.
 Object invoke(ELContext context, Object base, Object method, Class<?>[] paramTypes, Object[] params)
          If the base object is not null, invoke the method, with the given parameters on this bean.
 boolean isReadOnly(ELContext context, Object base, Object property)
          If the base object is not null, returns whether a call to setValue(ELContext, Object, Object, Object) will always fail.
 void setValue(ELContext context, Object base, Object property, Object value)
          If the base object is not null, attempts to set the value of the given property on this bean.
 
从类 java.lang.Object 继承的方法
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

构造方法详细信息

BeanELResolver

public BeanELResolver()
Creates a new read/write BeanELResolver.


BeanELResolver

public BeanELResolver(boolean readOnly)
Creates a new BeanELResolver whose read-only status is determined by the given parameter.

方法详细信息

getCommonPropertyType

public Class<?> getCommonPropertyType(ELContext context,
                                      Object base)
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.

指定者:
ELResolver 中的 getCommonPropertyType
参数:
context - The context of this evaluation.
base - The bean to analyze.
返回:
null if base is null; otherwise Object.class.

getFeatureDescriptors

public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context,
                                                         Object base)
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:

指定者:
ELResolver 中的 getFeatureDescriptors
参数:
context - The context of this evaluation.
base - The bean to analyze.
返回:
An Iterator containing zero or more FeatureDescriptor objects, each representing a property on this bean, or null if the base object is null.

getType

public Class<?> getType(ELContext context,
                        Object base,
                        Object property)
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.

指定者:
ELResolver 中的 getType
参数:
context - The context of this evaluation.
base - The bean to analyze.
property - The name of the property to analyze. Will be coerced to a String.
返回:
If the propertyResolved property of ELContext was set to true, then the most general acceptable type; otherwise undefined.
抛出:
NullPointerException - if context is null
PropertyNotFoundException - if base is not null and the specified property does not exist or is not readable.
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.

getValue

public Object getValue(ELContext context,
                       Object base,
                       Object property)
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.

指定者:
ELResolver 中的 getValue
参数:
context - The context of this evaluation.
base - The bean to analyze.
property - The name of the property to analyze. Will be coerced to a String.
返回:
If the propertyResolved property of ELContext was set to true, then the value of the given property. Otherwise, undefined.
抛出:
NullPointerException - if context is null
PropertyNotFoundException - if base is not null and the specified property does not exist or is not readable.
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.

isReadOnly

public boolean isReadOnly(ELContext context,
                          Object base,
                          Object property)
If the base object is not null, returns whether a call to 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.

指定者:
ELResolver 中的 isReadOnly
参数:
context - The context of this evaluation.
base - The bean to analyze.
property - The name of the property to analyze. Will be coerced to a String.
返回:
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.
抛出:
NullPointerException - if context is null
PropertyNotFoundException - if base is not null and the specified property does not exist or is not readable.
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.

setValue

public void setValue(ELContext context,
                     Object base,
                     Object property,
                     Object value)
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.

指定者:
ELResolver 中的 setValue
参数:
context - The context of this evaluation.
base - The bean to analyze.
property - The name of the property to analyze. Will be coerced to a String.
value - The value to be associated with the specified key.
抛出:
NullPointerException - if context is null
PropertyNotFoundException - if base is not null and the specified property does not exist or is not readable.
PropertyNotWritableException - if this resolver was constructed in read-only mode, or if there is no setter for the property
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.

invoke

public Object invoke(ELContext context,
                     Object base,
                     Object method,
                     Class<?>[] paramTypes,
                     Object[] params)
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.

覆盖:
ELResolver 中的 invoke
参数:
context - The context of this evaluation.
base - The bean on which to invoke the method
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.
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.
params - The parameters to pass to the method, or null if no parameters.
返回:
The result of the method invocation (null if the method has a void return type).
抛出:
MethodNotFoundException - if no suitable method can be found.
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.
从以下版本开始:
2.2


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