org.springframework.integration.expression.ValueExpression.java Source code

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Here is the source code for org.springframework.integration.expression.ValueExpression.java

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/*
 * Copyright 2014-2019 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.integration.expression;

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.util.Assert;

/**
 * A very simple hardcoded implementation of the {@link Expression} interface that represents an
 * immutable value. It is used as value holder in the context of expression evaluation.
 *
 * @param <V> - The expected value type.
 *
 * @author Artem Bilan
 * @author Gary Russell
 * @since 4.0
 */
public class ValueExpression<V> implements Expression {

    /** Fixed value of this expression */
    private final V value;

    private final Class<V> aClass;

    private final TypedValue typedResultValue;

    private final TypeDescriptor typeDescriptor;

    @SuppressWarnings("unchecked")
    public ValueExpression(V value) {
        Assert.notNull(value, "'value' must not be null");
        this.value = value;
        this.aClass = (Class<V>) this.value.getClass();
        this.typedResultValue = new TypedValue(this.value);
        this.typeDescriptor = this.typedResultValue.getTypeDescriptor();
    }

    @Override
    public V getValue() throws EvaluationException {
        return this.value;
    }

    @Override
    public V getValue(Object rootObject) throws EvaluationException {
        return this.value;
    }

    @Override
    public V getValue(EvaluationContext context) throws EvaluationException {
        return this.value;
    }

    @Override
    public V getValue(EvaluationContext context, Object rootObject) throws EvaluationException {
        return this.value;
    }

    @Override
    public <T> T getValue(Object rootObject, Class<T> desiredResultType) throws EvaluationException {
        return getValue(desiredResultType);
    }

    @Override
    public <T> T getValue(Class<T> desiredResultType) throws EvaluationException {
        return org.springframework.expression.common.ExpressionUtils.convertTypedValue(null, this.typedResultValue,
                desiredResultType);
    }

    @Override
    public <T> T getValue(EvaluationContext context, Object rootObject, Class<T> desiredResultType)
            throws EvaluationException {
        return getValue(context, desiredResultType);
    }

    @Override
    public <T> T getValue(EvaluationContext context, Class<T> desiredResultType) throws EvaluationException {
        return org.springframework.expression.common.ExpressionUtils.convertTypedValue(context,
                this.typedResultValue, desiredResultType);
    }

    @Override
    public Class<V> getValueType() throws EvaluationException {
        return this.aClass;
    }

    @Override
    public Class<V> getValueType(Object rootObject) throws EvaluationException {
        return this.aClass;
    }

    @Override
    public Class<V> getValueType(EvaluationContext context) throws EvaluationException {
        return this.aClass;
    }

    @Override
    public Class<V> getValueType(EvaluationContext context, Object rootObject) throws EvaluationException {
        return this.aClass;
    }

    @Override
    public TypeDescriptor getValueTypeDescriptor() throws EvaluationException {
        return this.typeDescriptor;
    }

    @Override
    public TypeDescriptor getValueTypeDescriptor(Object rootObject) throws EvaluationException {
        return this.typeDescriptor;
    }

    @Override
    public TypeDescriptor getValueTypeDescriptor(EvaluationContext context) throws EvaluationException {
        return this.typeDescriptor;
    }

    @Override
    public TypeDescriptor getValueTypeDescriptor(EvaluationContext context, Object rootObject)
            throws EvaluationException {
        return this.typeDescriptor;
    }

    @Override
    public boolean isWritable(EvaluationContext context) throws EvaluationException {
        return false;
    }

    @Override
    public boolean isWritable(EvaluationContext context, Object rootObject) throws EvaluationException {
        return false;
    }

    @Override
    public boolean isWritable(Object rootObject) throws EvaluationException {
        return false;
    }

    @Override
    public void setValue(EvaluationContext context, Object value) throws EvaluationException {
        setValue(context, null, value);
    }

    @Override
    public void setValue(Object rootObject, Object value) throws EvaluationException {
        setValue(null, rootObject, value);
    }

    @Override
    public void setValue(EvaluationContext context, Object rootObject, Object value) throws EvaluationException {
        throw new EvaluationException(this.value.toString(), "Cannot call setValue() on a ValueExpression");
    }

    @Override
    public String getExpressionString() {
        return this.value.toString();
    }

    @Override
    public String toString() {
        return "ValueExpression [value=" + this.value + "]";
    }

}