com.sun.el
类 MethodExpressionImpl

java.lang.Object
  javax.el.Expression
      javax.el.MethodExpression
          com.sun.el.MethodExpressionImpl

所有已实现的接口：

Externalizable, Serializable

public final class MethodExpressionImpl
extends MethodExpression
implements Externalizable

An Expression that refers to a method on an object.

The ExpressionFactory.createMethodExpression(javax.el.ELContext, java.lang.String, java.lang.Class, java.lang.Class[]) method can be used to parse an expression string and return a concrete instance of MethodExpression that encapsulates the parsed expression. The FunctionMapper is used at parse time, not evaluation time, so one is not needed to evaluate an expression using this class. However, the ELContext is needed at evaluation time.

The getMethodInfo(javax.el.ELContext) and invoke(javax.el.ELContext, java.lang.Object[]) methods will evaluate the expression each time they are called. The ELResolver in the ELContext is used to resolve the top-level variables and to determine the behavior of the . and [] operators. For any of the two methods, the ELResolver.getValue(javax.el.ELContext, java.lang.Object, java.lang.Object) method is used to resolve all properties up to but excluding the last one. This provides the base object on which the method appears. If the base object is null, a NullPointerException must be thrown. At the last resolution, the final property is then coerced to a String, which provides the name of the method to be found. A method matching the name and expected parameters provided at parse time is found and it is either queried or invoked (depending on the method called on this MethodExpression).

See the notes about comparison, serialization and immutability in the Expression javadocs.

版本：

$Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: hmalphett $

作者：

Jacob Hookom [jacob@hookom.net]

另请参见：

ELResolver, Expression, ExpressionFactory, MethodExpression, 序列化表格

构造方法摘要

MethodExpressionImpl()

MethodExpressionImpl(String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class expectedType, Class[] paramTypes)

方法摘要

boolean	equals(Object obj) Determines whether the specified object is equal to this Expression.
String	getExpressionString() Returns the original String used to create this Expression, unmodified.
MethodInfo	getMethodInfo(ELContext context) Evaluates the expression relative to the provided context, and returns information about the actual referenced method.
int	hashCode() Returns the hash code for this Expression.
Object	invoke(ELContext context, Object[] params) Evaluates the expression relative to the provided context, invokes the method that was found using the supplied parameters, and returns the result of the method invocation.
boolean	isLiteralText() Returns whether this expression was created from only literal text.
boolean	isParmetersProvided() Return whether this MethodExpression was created with parameters.
void	readExternal(ObjectInput in)
void	writeExternal(ObjectOutput out)

从类 java.lang.Object 继承的方法

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

构造方法详细信息

MethodExpressionImpl

public MethodExpressionImpl()

MethodExpressionImpl

public MethodExpressionImpl(String expr,
                            Node node,
                            FunctionMapper fnMapper,
                            VariableMapper varMapper,
                            Class expectedType,
                            Class[] paramTypes)

参数：

expr -

node -

fnMapper -

expectedType -

paramTypes -

方法详细信息

equals

public boolean equals(Object obj)

Determines whether the specified object is equal to this Expression.

The result is true if and only if the argument is not null, is an Expression object that is the of the same type (ValueExpression or MethodExpression), and has an identical parsed representation.

Note that two expressions can be equal if their expression Strings are different. For example, ${fn1:foo()} and ${fn2:foo()} are equal if their corresponding FunctionMappers mapped fn1:foo and fn2:foo to the same method.

指定者：

类 Expression 中的 equals

参数：

obj - the Object to test for equality.

返回：

true if obj equals this Expression; false otherwise.

另请参见：

Hashtable, Object.equals(java.lang.Object)

getExpressionString

public String getExpressionString()

Returns the original String used to create this Expression, unmodified.

This is used for debugging purposes but also for the purposes of comparison (e.g. to ensure the expression in a configuration file has not changed).

This method does not provide sufficient information to re-create an expression. Two different expressions can have exactly the same expression string but different function mappings. Serialization should be used to save and restore the state of an Expression.

指定者：

类 Expression 中的 getExpressionString

返回：

The original expression String.

另请参见：

Expression.getExpressionString()

getMethodInfo

public MethodInfo getMethodInfo(ELContext context)
                         throws PropertyNotFoundException,
                                MethodNotFoundException,
                                ELException

Evaluates the expression relative to the provided context, and returns information about the actual referenced method.

指定者：

类 MethodExpression 中的 getMethodInfo

参数：

context - The context of this evaluation

返回：

an instance of MethodInfo containing information about the method the expression evaluated to.

抛出：

NullPointerException - if context is null or the base object is null on the last resolution.

PropertyNotFoundException - if one of the property resolutions failed because a specified variable or property does not exist or is not readable.

MethodNotFoundException - if no suitable method can be found.

ELException - if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.

另请参见：

MethodExpression.getMethodInfo(javax.el.ELContext)

hashCode

public int hashCode()

Returns the hash code for this Expression.

See the note in the equals(java.lang.Object) method on how two expressions can be equal if their expression Strings are different. Recall that if two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result. Implementations must take special note and implement hashCode correctly.

指定者：

类 Expression 中的 hashCode

返回：

The hash code for this Expression.

另请参见：

equals(java.lang.Object), Hashtable, Object.hashCode()

invoke

public Object invoke(ELContext context,
                     Object[] params)
              throws PropertyNotFoundException,
                     MethodNotFoundException,
                     ELException

Evaluates the expression relative to the provided context, invokes the method that was found using the supplied parameters, and returns the result of the method invocation.

指定者：

类 MethodExpression 中的 invoke

参数：

context - The context of this evaluation.

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：

NullPointerException - if context is null or the base object is null on the last resolution.

PropertyNotFoundException - if one of the property resolutions failed because a specified variable or property does not exist or is not readable.

MethodNotFoundException - if no suitable method can be found.

ELException - if an exception was thrown while performing property or variable 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.

另请参见：

MethodExpression.invoke(javax.el.ELContext, java.lang.Object[])

readExternal

public void readExternal(ObjectInput in)
                  throws IOException,
                         ClassNotFoundException

指定者：

接口 Externalizable 中的 readExternal

抛出：

IOException

ClassNotFoundException

writeExternal

public void writeExternal(ObjectOutput out)
                   throws IOException

指定者：

接口 Externalizable 中的 writeExternal

抛出：

IOException

isLiteralText

public boolean isLiteralText()

从类 Expression 复制的描述

Returns whether this expression was created from only literal text.

This method must return true if and only if the expression string this expression was created from contained no unescaped EL delimeters (${...} or #{...}).

指定者：

类 Expression 中的 isLiteralText

返回：

true if this expression was created from only literal text; false otherwise.

isParmetersProvided

public boolean isParmetersProvided()

从类 MethodExpression 复制的描述

Return whether this MethodExpression was created with parameters.

This method must return true if and only if parameters are specified in the EL, using the expr-a.expr-b(...) syntax.

覆盖：

类 MethodExpression 中的 isParmetersProvided

返回：

true if the MethodExpression was created with parameters, false otherwise.