1 /*
2 * Copyright 2002-2013 the original author or authors.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package org.springframework.expression;
18
19 import java.util.List;
20
21 /**
22 * Expressions are executed in an evaluation context. It is in this context that
23 * references are resolved when encountered during expression evaluation.
24 *
25 * <p>There is a default implementation of the EvaluationContext,
26 * {@link org.springframework.expression.spel.support.StandardEvaluationContext} that can
27 * be extended, rather than having to implement everything.
28 *
29 * @author Andy Clement
30 * @author Juergen Hoeller
31 * @since 3.0
32 */
33 public interface EvaluationContext {
34
35 /**
36 * Return the default root context object against which unqualified
37 * properties/methods/etc should be resolved. This can be overridden
38 * when evaluating an expression.
39 */
40 TypedValue getRootObject();
41
42 /**
43 * Return a list of resolvers that will be asked in turn to locate a constructor.
44 */
45 List<ConstructorResolver> getConstructorResolvers();
46
47 /**
48 * Return a list of resolvers that will be asked in turn to locate a method.
49 */
50 List<MethodResolver> getMethodResolvers();
51
52 /**
53 * Return a list of accessors that will be asked in turn to read/write a property.
54 */
55 List<PropertyAccessor> getPropertyAccessors();
56
57 /**
58 * Return a type locator that can be used to find types, either by short or
59 * fully qualified name.
60 */
61 TypeLocator getTypeLocator();
62
63 /**
64 * Return a type converter that can convert (or coerce) a value from one type to another.
65 */
66 TypeConverter getTypeConverter();
67
68 /**
69 * Return a type comparator for comparing pairs of objects for equality.
70 */
71 TypeComparator getTypeComparator();
72
73 /**
74 * Return an operator overloader that may support mathematical operations
75 * between more than the standard set of types.
76 */
77 OperatorOverloader getOperatorOverloader();
78
79 /**
80 * Return a bean resolver that can look up beans by name.
81 */
82 BeanResolver getBeanResolver();
83
84 /**
85 * Set a named variable within this evaluation context to a specified value.
86 * @param name variable to set
87 * @param value value to be placed in the variable
88 */
89 void setVariable(String name, Object value);
90
91 /**
92 * Look up a named variable within this evaluation context.
93 * @param name variable to lookup
94 * @return the value of the variable
95 */
96 Object lookupVariable(String name);
97
98 }