Module jakarta.el
Package jakarta.el

Class ArrayELResolver

java.lang.Object
jakarta.el.ELResolver
jakarta.el.ArrayELResolver
public class ArrayELResolver extends ELResolver
Defines property resolution behavior on arrays.

This resolver handles base objects that are Java language arrays. It accepts the case sensitive string "length" or any other object as a property and coerces that object into an integer index into the array. The resulting value is the value in the array at that index.

This resolver can be constructed in read-only mode, which means that isReadOnly will always return true and setValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) will always throw PropertyNotWritableException.

ELResolvers are combined together using CompositeELResolvers, to define rich semantics for evaluating an expression. See the javadocs for ELResolver for details.

Since:
Jakarta Server Pages 2.1
See Also:

  • Constructor Details

    • ArrayELResolver

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

    • ArrayELResolver

      public ArrayELResolver(boolean isReadOnly)
      Creates a new ArrayELResolver whose read-only status is determined by the given parameter.
      Parameters:
      isReadOnly - true if this resolver cannot modify arrays; false otherwise.

  • Method Details

    • getType

      public Class<?> getType(ELContext context, Object base, Object property)
      If the base object is an array, returns the most general acceptable type for a value in this array.

      If the base is a array, 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.

      Assuming the base is an array, that this resolver was not constructed in read-only mode, and that the provided property can be coerced to a valid index for base array, this method will return base.getClass().getComponentType(), which is the most general type of component that can be stored at any given index in the array.

      Specified by:
      getType in class ELResolver
      Parameters:
      context - The context of this evaluation.
      base - The array to analyze. Only bases that are Java language arrays are handled by this resolver.
      property - The case sensitive string "length" or the index of the element in the array to return the acceptable type for. If not the case sensitive string "length", will be coerced into an integer and checked if it is a valid index for the array, but otherwise ignored by this resolver.
      Returns:
      If the propertyResolved property of ELContext was set to true, then the most general acceptable type which must be null if the either the property or the resolver is read-only; otherwise undefined
      Throws:
      PropertyNotFoundException - if the given index is out of bounds for this array.
      NullPointerException - if context is null
      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 a Java language array, returns the length of the array or the value at the given index. If the property argument is the case sensitive string "length", then the length of the array is returned. Otherwise, the property argument is coerced into an integer and used as the index of the value to be returned. If the coercion could not be performed, an IllegalArgumentException is thrown. If the index is out of bounds, null is returned.

      If the base is a Java language array, 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.

      Specified by:
      getValue in class ELResolver
      Parameters:
      context - The context of this evaluation.
      base - The array to analyze. Only bases that are Java language arrays are handled by this resolver.
      property - Either the string "length" or the index of the value to be returned. An index value will be coerced into an integer.
      Returns:
      If the propertyResolved property of ELContext was set to true, then the length of the array, the value at the given index or null if the index was out of bounds. Otherwise, undefined.
      Throws:
      IllegalArgumentException - if the property was not the string "length" and could not be coerced into an integer.
      NullPointerException - if context is null.
      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 val)
      If the base object is a Java language array and the property is not the case sensitive string length, attempts to set the value at the given index with the given value. The index is specified by the property argument, and coerced into an integer. If the coercion could not be performed, an IllegalArgumentException is thrown. If the index is out of bounds, a PropertyNotFoundException is thrown.

      If the base is a Java language array, 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 or the property is the case sensitive string length, this method will always throw PropertyNotWritableException.

      Specified by:
      setValue in class ELResolver
      Parameters:
      context - The context of this evaluation.
      base - The array to be modified. Only bases that are Java language arrays are handled by this resolver.
      property - The case sensitive string length or an object to coerce to an integer to provide the index of the value to be set.
      val - The value to be set at the given index.
      Throws:
      ClassCastException - if the class of the specified element prevents it from being added to this array.
      NullPointerException - if context is null.
      IllegalArgumentException - if the property could not be coerced into an integer, or if some aspect of the specified element prevents it from being added to this array.
      PropertyNotWritableException - if this resolver was constructed in read-only mode or the property was the case sensitive string length.
      PropertyNotFoundException - if the given index is out of bounds for this array.
      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 a Java language array, returns whether a call to setValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) will always fail.

      If the base is a Java language array, 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 this resolver was constructed in read-only mode or the property is the case sensitive string length, this method will always return true. Otherwise, it returns false.

      Specified by:
      isReadOnly in class ELResolver
      Parameters:
      context - The context of this evaluation.
      base - The array to analyze. Only bases that are a Java language array are handled by this resolver.
      property - The case sensitive string length or an object to coerce to an integer to provide the index to check if an attempt to call setValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) with that index will always fail.
      Returns:
      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:
      PropertyNotFoundException - if the given index is out of bounds for this array.
      NullPointerException - if context is null
      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.

    • getCommonPropertyType

      public Class<?> getCommonPropertyType(ELContext context, Object base)
      If the base object is a Java language array, returns the most general type that this resolver accepts for the property argument. Otherwise, returns null.

      Assuming the base is an array, this method will always return Integer.class. This is because arrays accept integers for their index.

      Specified by:
      getCommonPropertyType in class ELResolver
      Parameters:
      context - The context of this evaluation.
      base - The array to analyze. Only bases that are a Java language array are handled by this resolver.
      Returns:
      null if base is not a Java language array; otherwise Integer.class.