1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package javax.servlet.jsp.el;
/**
* <p>The abstract base class for an expression-language evaluator.
* Classes that implement an expression language expose their functionality
* via this abstract class.</p>
*
* <p>An instance of the ExpressionEvaluator can be obtained via the
* JspContext / PageContext</p>
*
* <p>The parseExpression() and evaluate() methods must be thread-safe.
* That is, multiple threads may call these methods on the same
* ExpressionEvaluator object simultaneously. Implementations should
* synchronize access if they depend on transient state. Implementations
* should not, however, assume that only one object of each
* ExpressionEvaluator type will be instantiated; global caching should
* therefore be static.</p>
*
* <p>Only a single EL expression, starting with '${' and ending with
* '}', can be parsed or evaluated at a time. EL expressions
* cannot be mixed with static text. For example, attempting to
* parse or evaluate "<code>abc${1+1}def${1+1}ghi</code>" or even
* "<code>${1+1}${1+1}</code>" will cause an <code>ELException</code> to
* be thrown.</p>
*
* <p>The following are examples of syntactically legal EL expressions:
*
* <ul>
* <li><code>${person.lastName}</code></li>
* <li><code>${8 * 8}</code></li>
* <li><code>${my:reverse('hello')}</code></li>
* </ul>
* </p>
*
* @since 2.0
* @deprecated As of JSP 2.1, replaced by javax.el.ExpressionFactory
*/
@SuppressWarnings("dep-ann") // TCK signature test fails with annotation
public abstract class ExpressionEvaluator {
/**
* Prepare an expression for later evaluation. This method should perform
* syntactic validation of the expression; if in doing so it detects
* errors, it should raise an ELParseException.
*
* @param expression The expression to be evaluated.
* @param expectedType The expected type of the result of the evaluation
* @param fMapper A FunctionMapper to resolve functions found in
* the expression. It can be null, in which case no functions
* are supported for this invocation. The ExpressionEvaluator
* must not hold on to the FunctionMapper reference after
* returning from <code>parseExpression()</code>. The
* <code>Expression</code> object returned must invoke the same
* functions regardless of whether the mappings in the
* provided <code>FunctionMapper</code> instance change between
* calling <code>ExpressionEvaluator.parseExpression()</code>
* and <code>Expression.evaluate()</code>.
* @return The Expression object encapsulating the arguments.
*
* @exception ELException Thrown if parsing errors were found.
*/
public abstract Expression parseExpression( String expression,
@SuppressWarnings("unchecked") // TCK signature fails with generics
Class expectedType,
FunctionMapper fMapper)
throws ELException;
/**
* Evaluates an expression. This method may perform some syntactic
* validation and, if so, it should raise an ELParseException error if
* it encounters syntactic errors. EL evaluation errors should cause
* an ELException to be raised.
*
* @param expression The expression to be evaluated.
* @param expectedType The expected type of the result of the evaluation
* @param vResolver A VariableResolver instance that can be used at
* runtime to resolve the name of implicit objects into Objects.
* @param fMapper A FunctionMapper to resolve functions found in
* the expression. It can be null, in which case no functions
* are supported for this invocation.
* @return The result of the expression evaluation.
*
* @exception ELException Thrown if the expression evaluation failed.
*/
public abstract Object evaluate( String expression,
@SuppressWarnings("unchecked") // TCK signature fails with generics
Class expectedType,
VariableResolver vResolver,
FunctionMapper fMapper)
throws ELException;
}
|
