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Spring Expression Language (SpEL)
/*
* Copyright 2002-2017 the original author or authors.
*
* Licensed 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
*
* https://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 org.springframework.expression;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.lang.Nullable;
/**
* An expression capable of evaluating itself against context objects.
* Encapsulates the details of a previously parsed expression string.
* Provides a common abstraction for expression evaluation.
*
* @author Keith Donald
* @author Andy Clement
* @author Juergen Hoeller
* @since 3.0
*/
public interface Expression {
/**
* Return the original string used to create this expression (unmodified).
* @return the original expression string
*/
String getExpressionString();
/**
* Evaluate this expression in the default standard context.
* @return the evaluation result
* @throws EvaluationException if there is a problem during evaluation
*/
@Nullable
Object getValue() throws EvaluationException;
/**
* Evaluate the expression in the default context. If the result
* of the evaluation does not match (and cannot be converted to)
* the expected result type then an exception will be returned.
* @param desiredResultType the class the caller would like the result to be
* @return the evaluation result
* @throws EvaluationException if there is a problem during evaluation
*/
@Nullable
T getValue(@Nullable Class desiredResultType) throws EvaluationException;
/**
* Evaluate this expression against the specified root object.
* @param rootObject the root object against which to evaluate the expression
* @return the evaluation result
* @throws EvaluationException if there is a problem during evaluation
*/
@Nullable
Object getValue(@Nullable Object rootObject) throws EvaluationException;
/**
* Evaluate the expression in the default context against the specified root
* object. If the result of the evaluation does not match (and cannot be
* converted to) the expected result type then an exception will be returned.
* @param rootObject the root object against which to evaluate the expression
* @param desiredResultType the class the caller would like the result to be
* @return the evaluation result
* @throws EvaluationException if there is a problem during evaluation
*/
@Nullable
T getValue(@Nullable Object rootObject, @Nullable Class desiredResultType) throws EvaluationException;
/**
* Evaluate this expression in the provided context and return the result
* of evaluation.
* @param context the context in which to evaluate the expression
* @return the evaluation result
* @throws EvaluationException if there is a problem during evaluation
*/
@Nullable
Object getValue(EvaluationContext context) throws EvaluationException;
/**
* Evaluate this expression in the provided context and return the result
* of evaluation, but use the supplied root context as an override for any
* default root object specified in the context.
* @param context the context in which to evaluate the expression
* @param rootObject the root object against which to evaluate the expression
* @return the evaluation result
* @throws EvaluationException if there is a problem during evaluation
*/
@Nullable
Object getValue(EvaluationContext context, @Nullable Object rootObject) throws EvaluationException;
/**
* Evaluate the expression in a specified context which can resolve references
* to properties, methods, types, etc. The type of the evaluation result is
* expected to be of a particular class and an exception will be thrown if it
* is not and cannot be converted to that type.
* @param context the context in which to evaluate the expression
* @param desiredResultType the class the caller would like the result to be
* @return the evaluation result
* @throws EvaluationException if there is a problem during evaluation
*/
@Nullable
T getValue(EvaluationContext context, @Nullable Class desiredResultType) throws EvaluationException;
/**
* Evaluate the expression in a specified context which can resolve references
* to properties, methods, types, etc. The type of the evaluation result is
* expected to be of a particular class and an exception will be thrown if it
* is not and cannot be converted to that type. The supplied root object
* overrides any default specified on the supplied context.
* @param context the context in which to evaluate the expression
* @param rootObject the root object against which to evaluate the expression
* @param desiredResultType the class the caller would like the result to be
* @return the evaluation result
* @throws EvaluationException if there is a problem during evaluation
*/
@Nullable
T getValue(EvaluationContext context, @Nullable Object rootObject, @Nullable Class desiredResultType)
throws EvaluationException;
/**
* Return the most general type that can be passed to a {@link #setValue}
* method using the default context.
* @return the most general type of value that can be set on this context
* @throws EvaluationException if there is a problem determining the type
*/
@Nullable
Class getValueType() throws EvaluationException;
/**
* Return the most general type that can be passed to the
* {@link #setValue(Object, Object)} method using the default context.
* @param rootObject the root object against which to evaluate the expression
* @return the most general type of value that can be set on this context
* @throws EvaluationException if there is a problem determining the type
*/
@Nullable
Class getValueType(@Nullable Object rootObject) throws EvaluationException;
/**
* Return the most general type that can be passed to the
* {@link #setValue(EvaluationContext, Object)} method for the given context.
* @param context the context in which to evaluate the expression
* @return the most general type of value that can be set on this context
* @throws EvaluationException if there is a problem determining the type
*/
@Nullable
Class getValueType(EvaluationContext context) throws EvaluationException;
/**
* Return the most general type that can be passed to the
* {@link #setValue(EvaluationContext, Object, Object)} method for the given
* context. The supplied root object overrides any specified in the context.
* @param context the context in which to evaluate the expression
* @param rootObject the root object against which to evaluate the expression
* @return the most general type of value that can be set on this context
* @throws EvaluationException if there is a problem determining the type
*/
@Nullable
Class getValueType(EvaluationContext context, @Nullable Object rootObject) throws EvaluationException;
/**
* Return the most general type that can be passed to a {@link #setValue}
* method using the default context.
* @return a type descriptor for values that can be set on this context
* @throws EvaluationException if there is a problem determining the type
*/
@Nullable
TypeDescriptor getValueTypeDescriptor() throws EvaluationException;
/**
* Return the most general type that can be passed to the
* {@link #setValue(Object, Object)} method using the default context.
* @param rootObject the root object against which to evaluate the expression
* @return a type descriptor for values that can be set on this context
* @throws EvaluationException if there is a problem determining the type
*/
@Nullable
TypeDescriptor getValueTypeDescriptor(@Nullable Object rootObject) throws EvaluationException;
/**
* Return the most general type that can be passed to the
* {@link #setValue(EvaluationContext, Object)} method for the given context.
* @param context the context in which to evaluate the expression
* @return a type descriptor for values that can be set on this context
* @throws EvaluationException if there is a problem determining the type
*/
@Nullable
TypeDescriptor getValueTypeDescriptor(EvaluationContext context) throws EvaluationException;
/**
* Return the most general type that can be passed to the
* {@link #setValue(EvaluationContext, Object, Object)} method for the given
* context. The supplied root object overrides any specified in the context.
* @param context the context in which to evaluate the expression
* @param rootObject the root object against which to evaluate the expression
* @return a type descriptor for values that can be set on this context
* @throws EvaluationException if there is a problem determining the type
*/
@Nullable
TypeDescriptor getValueTypeDescriptor(EvaluationContext context, @Nullable Object rootObject) throws EvaluationException;
/**
* Determine if an expression can be written to, i.e. setValue() can be called.
* @param rootObject the root object against which to evaluate the expression
* @return {@code true} if the expression is writable; {@code false} otherwise
* @throws EvaluationException if there is a problem determining if it is writable
*/
boolean isWritable(@Nullable Object rootObject) throws EvaluationException;
/**
* Determine if an expression can be written to, i.e. setValue() can be called.
* @param context the context in which the expression should be checked
* @return {@code true} if the expression is writable; {@code false} otherwise
* @throws EvaluationException if there is a problem determining if it is writable
*/
boolean isWritable(EvaluationContext context) throws EvaluationException;
/**
* Determine if an expression can be written to, i.e. setValue() can be called.
* The supplied root object overrides any specified in the context.
* @param context the context in which the expression should be checked
* @param rootObject the root object against which to evaluate the expression
* @return {@code true} if the expression is writable; {@code false} otherwise
* @throws EvaluationException if there is a problem determining if it is writable
*/
boolean isWritable(EvaluationContext context, @Nullable Object rootObject) throws EvaluationException;
/**
* Set this expression in the provided context to the value provided.
* @param rootObject the root object against which to evaluate the expression
* @param value the new value
* @throws EvaluationException if there is a problem during evaluation
*/
void setValue(@Nullable Object rootObject, @Nullable Object value) throws EvaluationException;
/**
* Set this expression in the provided context to the value provided.
* @param context the context in which to set the value of the expression
* @param value the new value
* @throws EvaluationException if there is a problem during evaluation
*/
void setValue(EvaluationContext context, @Nullable Object value) throws EvaluationException;
/**
* Set this expression in the provided context to the value provided.
* The supplied root object overrides any specified in the context.
* @param context the context in which to set the value of the expression
* @param rootObject the root object against which to evaluate the expression
* @param value the new value
* @throws EvaluationException if there is a problem during evaluation
*/
void setValue(EvaluationContext context, @Nullable Object rootObject, @Nullable Object value) throws EvaluationException;
}