/*
 * 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.
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package org.springframework.expression.common;

import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.Expression;
import org.springframework.expression.TypedValue;
import org.springframework.lang.Nullable;

A very simple hardcoded implementation of the Expression interface that represents a string literal. It is used with CompositeStringExpression when representing a template expression which is made up of pieces - some being real expressions to be handled by an EL implementation like SpEL, and some being just textual elements.
Author:Andy Clement, Juergen Hoeller
Since:3.0
/** * A very simple hardcoded implementation of the Expression interface that represents a * string literal. It is used with CompositeStringExpression when representing a template * expression which is made up of pieces - some being real expressions to be handled by * an EL implementation like SpEL, and some being just textual elements. * * @author Andy Clement * @author Juergen Hoeller * @since 3.0 */
public class LiteralExpression implements Expression {
Fixed literal value of this expression.
/** Fixed literal value of this expression. */
private final String literalValue; public LiteralExpression(String literalValue) { this.literalValue = literalValue; } @Override public final String getExpressionString() { return this.literalValue; } @Override public Class<?> getValueType(EvaluationContext context) { return String.class; } @Override public String getValue() { return this.literalValue; } @Override @Nullable public <T> T getValue(@Nullable Class<T> expectedResultType) throws EvaluationException { Object value = getValue(); return ExpressionUtils.convertTypedValue(null, new TypedValue(value), expectedResultType); } @Override public String getValue(@Nullable Object rootObject) { return this.literalValue; } @Override @Nullable public <T> T getValue(@Nullable Object rootObject, @Nullable Class<T> desiredResultType) throws EvaluationException { Object value = getValue(rootObject); return ExpressionUtils.convertTypedValue(null, new TypedValue(value), desiredResultType); } @Override public String getValue(EvaluationContext context) { return this.literalValue; } @Override @Nullable public <T> T getValue(EvaluationContext context, @Nullable Class<T> expectedResultType) throws EvaluationException { Object value = getValue(context); return ExpressionUtils.convertTypedValue(context, new TypedValue(value), expectedResultType); } @Override public String getValue(EvaluationContext context, @Nullable Object rootObject) throws EvaluationException { return this.literalValue; } @Override @Nullable public <T> T getValue(EvaluationContext context, @Nullable Object rootObject, @Nullable Class<T> desiredResultType) throws EvaluationException { Object value = getValue(context, rootObject); return ExpressionUtils.convertTypedValue(context, new TypedValue(value), desiredResultType); } @Override public Class<?> getValueType() { return String.class; } @Override public Class<?> getValueType(@Nullable Object rootObject) throws EvaluationException { return String.class; } @Override public Class<?> getValueType(EvaluationContext context, @Nullable Object rootObject) throws EvaluationException { return String.class; } @Override public TypeDescriptor getValueTypeDescriptor() { return TypeDescriptor.valueOf(String.class); } @Override public TypeDescriptor getValueTypeDescriptor(@Nullable Object rootObject) throws EvaluationException { return TypeDescriptor.valueOf(String.class); } @Override public TypeDescriptor getValueTypeDescriptor(EvaluationContext context) { return TypeDescriptor.valueOf(String.class); } @Override public TypeDescriptor getValueTypeDescriptor(EvaluationContext context, @Nullable Object rootObject) throws EvaluationException { return TypeDescriptor.valueOf(String.class); } @Override public boolean isWritable(@Nullable Object rootObject) throws EvaluationException { return false; } @Override public boolean isWritable(EvaluationContext context) { return false; } @Override public boolean isWritable(EvaluationContext context, @Nullable Object rootObject) throws EvaluationException { return false; } @Override public void setValue(@Nullable Object rootObject, @Nullable Object value) throws EvaluationException { throw new EvaluationException(this.literalValue, "Cannot call setValue() on a LiteralExpression"); } @Override public void setValue(EvaluationContext context, @Nullable Object value) throws EvaluationException { throw new EvaluationException(this.literalValue, "Cannot call setValue() on a LiteralExpression"); } @Override public void setValue(EvaluationContext context, @Nullable Object rootObject, @Nullable Object value) throws EvaluationException { throw new EvaluationException(this.literalValue, "Cannot call setValue() on a LiteralExpression"); } }