org.springframework.expression.spel.SpelNode Maven / Gradle / Ivy
/*
* Copyright 2002-2018 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.spel;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.TypedValue;
import org.springframework.lang.Nullable;
/**
* Represents a node in the AST for a parsed expression.
*
* @author Andy Clement
* @since 3.0
*/
public interface SpelNode {
/**
* Evaluate the expression node in the context of the supplied expression state
* and return the value.
* @param expressionState the current expression state (includes the context)
* @return the value of this node evaluated against the specified state
*/
@Nullable
Object getValue(ExpressionState expressionState) throws EvaluationException;
/**
* Evaluate the expression node in the context of the supplied expression state
* and return the typed value.
* @param expressionState the current expression state (includes the context)
* @return the type value of this node evaluated against the specified state
*/
TypedValue getTypedValue(ExpressionState expressionState) throws EvaluationException;
/**
* Determine if this expression node will support a setValue() call.
* @param expressionState the current expression state (includes the context)
* @return true if the expression node will allow setValue()
* @throws EvaluationException if something went wrong trying to determine
* if the node supports writing
*/
boolean isWritable(ExpressionState expressionState) throws EvaluationException;
/**
* Evaluate the expression to a node and then set the new value on that node.
* For example, if the expression evaluates to a property reference, then the
* property will be set to the new value.
* @param expressionState the current expression state (includes the context)
* @param newValue the new value
* @throws EvaluationException if any problem occurs evaluating the expression or
* setting the new value
*/
void setValue(ExpressionState expressionState, @Nullable Object newValue) throws EvaluationException;
/**
* Return the string form of this AST node.
* @return the string form
*/
String toStringAST();
/**
* Return the number of children under this node.
* @return the child count
*/
int getChildCount();
/**
* Helper method that returns a SpelNode rather than an Antlr Tree node.
* @return the child node cast to a SpelNode
*/
SpelNode getChild(int index);
/**
* Determine the class of the object passed in, unless it is already a class object.
* @param obj the object that the caller wants the class of
* @return the class of the object if it is not already a class object,
* or {@code null} if the object is {@code null}
*/
@Nullable
Class getObjectClass(@Nullable Object obj);
/**
* Return the start position of this AST node in the expression string.
* @return the start position
*/
int getStartPosition();
/**
* Return the end position of this AST node in the expression string.
* @return the end position
*/
int getEndPosition();
}