ValueExpression (Apache Tomcat 7.0.108 API Documentation)

javax.el

## Class ValueExpression

- java.lang.Object
- - javax.el.Expression
  - - javax.el.ValueExpression

- All Implemented Interfaces:
    Serializable
  Direct Known Subclasses:
    JspValueExpression, ValueExpressionImpl, ValueExpressionLiteral

      public abstract class ValueExpression
      extends Expression

  See Also:
    Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `ValueExpression()`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `abstract Class<?>` | `getExpectedType()`
    `abstract Class<?>` | `getType(ELContext context)`
    `abstract Object` | `getValue(ELContext context)`
    `ValueReference` | `getValueReference(ELContext context)`
    `abstract boolean` | `isReadOnly(ELContext context)`
    `abstract void` | `setValue(ELContext context, Object value)`

    - ### Methods inherited from class javax.el.Expression

      `equals, getExpressionString, hashCode, isLiteralText`

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### ValueExpression

          public ValueExpression()

  - ### Method Detail

    - #### getValue

          public abstract Object getValue(ELContext context)

      Parameters:
        `context` - The EL context for this evaluation
      Returns:
        The result of evaluating this value expression
      Throws:
        `NullPointerException` - If the supplied context is `null`
        `PropertyNotFoundException` - If a property/variable resolution failed because no match was found or a match was found but was not readable
        `ELException` - Wraps any exception throw whilst resolving a property or variable

    - #### setValue

          public abstract void setValue(ELContext context,
                      Object value)

      Parameters:
        `context` - The EL context for this evaluation
        `value` - The value to set the property to which this value expression refers
      Throws:
        `NullPointerException` - If the supplied context is `null`
        `PropertyNotFoundException` - If a property/variable resolution failed because no match was found
        `PropertyNotWritableException` - If a property/variable resolution failed because a match was found but was not writable
        `ELException` - Wraps any exception throw whilst resolving a property or variable

    - #### isReadOnly

          public abstract boolean isReadOnly(ELContext context)

      Parameters:
        `context` - The EL context for this evaluation
      Returns:
        `true` if this expression is read only otherwise `false`
      Throws:
        `NullPointerException` - If the supplied context is `null`
        `PropertyNotFoundException` - If a property/variable resolution failed because no match was found or a match was found but was not readable
        `ELException` - Wraps any exception throw whilst resolving a property or variable

    - #### getType

          public abstract Class<?> getType(ELContext context)

      Parameters:
        `context` - The EL context for this evaluation
      Returns:
        The type of the result of this value expression
      Throws:
        `NullPointerException` - If the supplied context is `null`
        `PropertyNotFoundException` - If a property/variable resolution failed because no match was found or a match was found but was not readable
        `ELException` - Wraps any exception throw whilst resolving a property or variable

    - #### getExpectedType

          public abstract Class<?> getExpectedType()

    - #### getValueReference

          public ValueReference getValueReference(ELContext context)

      Parameters:
        `context` - The EL context for this evaluation
      Returns:
        This default implementation always returns `null`
      Since:
        EL 2.2

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