Package jakarta.el

Class StaticFieldELResolver

java.lang.Object
jakarta.el.ELResolver
jakarta.el.StaticFieldELResolver
public class StaticFieldELResolver extends ELResolver
An ELResolver for resolving static fields, enum constants and static methods. Also handles constructor calls as a special case.

The resolver handles base objects of the type ELClass, which is usually generated by a Jakarta Expression Language implementation.

Since:
Jakarta Expression Language 3.0
See Also:

  • Constructor Details

    • StaticFieldELResolver

      public StaticFieldELResolver()

  • Method Details

    • getValue

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

      Returns the value of a static field.

      If the base object is an instance of ELClass and the property is String, 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.

      If the property is a public static field of class specified in ELClass, return the value of the static field. An Enum constant is a public static field of an Enum object, and is a special case of this.
      Specified by:
      getValue in class ELResolver
      Parameters:
      context - The context of this evaluation.
      base - An ELClass.
      property - A static field name.
      Returns:
      If the propertyResolved property of ELContext was set to true, then the static field value.
      Throws:
      NullPointerException - if context is null.
      PropertyNotFoundException - if the specified class does not exist, or if the field is not a public static filed of the class, or if the field is inaccessible.

    • setValue

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

      Attempts to write to a static field.

      If the base object is an instance of ELClassand the property is String, a PropertyNotWritableException will always be thrown, because writing to a static field is not allowed.

      Specified by:
      setValue in class ELResolver
      Parameters:
      context - The context of this evaluation.
      base - An ELClass
      property - The name of the field
      value - The value to set the field of the class to.
      Throws:
      NullPointerException - if context is null
      PropertyNotWritableException - if base object instance of ELClassand property instance of String

    • invoke

      public Object invoke(ELContext context, Object base, Object methodName, Class<?>[] paramTypes, Object[] params)
      Invokes a public static method or the constructor for a class.

      If the base object is an instance of ELClass and the method is a String, the propertyResolved property of the ELContext object must be set to true by the resolver, before returning. If this property is not true after this method is called, the caller should ignore the return value.

      Invoke the public static method specified by method.

      The process involved in the method selection is the same as that used in BeanELResolver.

      As a special case, if the name of the method is "<init>", the constructor for the class will be invoked.

      Overrides:
      invoke in class ELResolver
      Parameters:
      base - An ELClass
      methodName - When coerced to a String, the simple name of the method.
      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.
      context - The context of this evaluation.
      Returns:
      The result of the method invocation (null if the method has a void return type).
      Throws:
      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.

    • getType

      public Class<?> getType(ELContext context, Object base, Object property)
      Returns the type of a static field.

      If the base object is an instance of ELClassand the property is a String, the propertyResolved property of the ELContext object must be set to true by the resolver, before returning. If this property is not true after this method is called, the caller can safely assume no value has been set.

      If the property string is a public static field of class specified in ELClass, return the type of the static field.

      Specified by:
      getType in class ELResolver
      Parameters:
      context - The context of this evaluation.
      base - An ELClass.
      property - The name of the field.
      Returns:
      If the propertyResolved property of ELContext was set to true, then the type of the type of the field.
      Throws:
      NullPointerException - if context is null.
      PropertyNotFoundException - if field is not a public static filed of the class, or if the field is inaccessible.

    • isReadOnly

      public boolean isReadOnly(ELContext context, Object base, Object property)

      Inquires whether the static field is writable.

      If the base object is an instance of ELClassand the property is a String, the propertyResolved property of the ELContext object must be set to true by the resolver, before returning. If this property is not true after this method is called, the caller can safely assume no value has been set.

      Always returns a true because writing to a static field is not allowed.

      Specified by:
      isReadOnly in class ELResolver
      Parameters:
      context - The context of this evaluation.
      base - An ELClass.
      property - The name of the bean.
      Returns:
      true
      Throws:
      NullPointerException - if context is null.

    • getFeatureDescriptors

      public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base)
      Returns the properties that can be resolved. Always returns null, since there is no reason to iterate through a list of one element: field name.
      Specified by:
      getFeatureDescriptors in class ELResolver
      Parameters:
      context - The context of this evaluation.
      base - An ELClass.
      Returns:
      null.
      See Also:

    • getCommonPropertyType

      public Class<?> getCommonPropertyType(ELContext context, Object base)
      Returns the type of the property. Always returns String.class, since a field name is a String.
      Specified by:
      getCommonPropertyType in class ELResolver
      Parameters:
      context - The context of this evaluation.
      base - An ELClass.
      Returns:
      String.class.