Quelle ValueExpressionImpl.java Sprache: JAVA

/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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
*
* http://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.apache.el;

import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

import jakarta.el.ELContext;
import jakarta.el.ELException;
import jakarta.el.FunctionMapper;
import jakarta.el.PropertyNotFoundException;
import jakarta.el.PropertyNotWritableException;
import jakarta.el.ValueExpression;
import jakarta.el.ValueReference;
import jakarta.el.VariableMapper;

import org.apache.el.lang.EvaluationContext;
import org.apache.el.lang.ExpressionBuilder;
import org.apache.el.parser.AstLiteralExpression;
import org.apache.el.parser.Node;
import org.apache.el.util.ReflectionUtil;

/**
* An <code>Expression</code> that can get or set a value.
*
* 
* In previous incarnations of this API, expressions could only be read.
* <code>ValueExpression</code> objects can now be used both to retrieve a
* value and to set a value. Expressions that can have a value set on them are
* referred to as l-value expressions. Those that cannot are referred to as
* r-value expressions. Not all r-value expressions can be used as l-value
* expressions (e.g. <code>"${1+1}"</code> or
* <code>"${firstName} ${lastName}"</code>). See the EL Specification for
* details. Expressions that cannot be used as l-values must always return
* <code>true</code> from <code>isReadOnly()</code>.
* 
*
* 
* The {@link jakarta.el.ExpressionFactory#createValueExpression} method
* can be used to parse an expression string and return a concrete instance
* of <code>ValueExpression</code> that encapsulates the parsed expression.
* The {@link FunctionMapper} is used at parse time, not evaluation time,
* so one is not needed to evaluate an expression using this class.
* However, the {@link ELContext} is needed at evaluation time.
*
* The {@link #getValue}, {@link #setValue}, {@link #isReadOnly} and
* {@link #getType} methods will evaluate the expression each time they are
* called. The {@link jakarta.el.ELResolver} in the <code>ELContext</code> is used
* to resolve the top-level variables and to determine the behavior of the
* <code>.</code> and <code>[]</code> operators. For any of the four methods,
* the {@link jakarta.el.ELResolver#getValue} method is used to resolve all
* properties up to but excluding the last one. This provides the
* <code>base</code> object. At the last resolution, the
* <code>ValueExpression</code> will call the corresponding
* {@link jakarta.el.ELResolver#getValue}, {@link jakarta.el.ELResolver#setValue},
* {@link jakarta.el.ELResolver#isReadOnly} or {@link jakarta.el.ELResolver#getType}
* method, depending on which was called on the <code>ValueExpression</code>.
* 
*
* See the notes about comparison, serialization and immutability in
* the {@link jakarta.el.Expression} javadocs.
*
* @see jakarta.el.ELResolver
* @see jakarta.el.Expression
* @see jakarta.el.ExpressionFactory
* @see jakarta.el.ValueExpression
*
* @author Jacob Hookom [jacob@hookom.net]
*/
public final class ValueExpressionImpl extends ValueExpression implements
 Externalizable {

 private Class<?> expectedType;

 private String expr;

 private FunctionMapper fnMapper;

 private VariableMapper varMapper;

 private transient Node node;

 public ValueExpressionImpl() {
 super();
 }

 public ValueExpressionImpl(String expr, Node node, FunctionMapper fnMapper,
 VariableMapper varMapper, Class<?> expectedType) {
 this.expr = expr;
 this.node = node;
 this.fnMapper = fnMapper;
 this.varMapper = varMapper;
 this.expectedType = expectedType;
 }

 /*
 * (non-Javadoc)
 *
 * @see java.lang.Object#equals(java.lang.Object)
 */
 @Override
 public boolean equals(Object obj) {
 if (!(obj instanceof ValueExpressionImpl)) {
 return false;
 }
 if (obj.hashCode() != this.hashCode()) {
 return false;
 }

 return this.getNode().equals(((ValueExpressionImpl) obj).getNode());
 }

 /*
 * (non-Javadoc)
 *
 * @see jakarta.el.ValueExpression#getExpectedType()
 */
 @Override
 public Class<?> getExpectedType() {
 return this.expectedType;
 }

 /**
 * Returns the type the result of the expression will be coerced to after
 * evaluation.
 *
 * @return the <code>expectedType</code> passed to the
 * <code>ExpressionFactory.createValueExpression</code> method
 * that created this <code>ValueExpression</code>.
 *
 * @see jakarta.el.Expression#getExpressionString()
 */
 @Override
 public String getExpressionString() {
 return this.expr;
 }

 private Node getNode() throws ELException {
 if (this.node == null) {
 this.node = ExpressionBuilder.createNode(this.expr);
 }
 return this.node;
 }

 /*
 * (non-Javadoc)
 *
 * @see jakarta.el.ValueExpression#getType(jakarta.el.ELContext)
 */
 @Override
 public Class<?> getType(ELContext context) throws PropertyNotFoundException,
 ELException {
 EvaluationContext ctx = new EvaluationContext(context, this.fnMapper,
 this.varMapper);
 context.notifyBeforeEvaluation(getExpressionString());
 Class<?> result = this.getNode().getType(ctx);
 context.notifyAfterEvaluation(getExpressionString());
 return result;
 }

 /*
 * (non-Javadoc)
 *
 * @see jakarta.el.ValueExpression#getValue(jakarta.el.ELContext)
 */
 @SuppressWarnings("unchecked")
 @Override
 public <T> T getValue(ELContext context) throws PropertyNotFoundException,
 ELException {
 EvaluationContext ctx = new EvaluationContext(context, this.fnMapper,
 this.varMapper);
 context.notifyBeforeEvaluation(getExpressionString());
 Object value = this.getNode().getValue(ctx);
 if (this.expectedType != null) {
 value = context.convertToType(value, this.expectedType);
 }
 context.notifyAfterEvaluation(getExpressionString());
 return (T) value;
 }

 /*
 * (non-Javadoc)
 *
 * @see java.lang.Object#hashCode()
 */
 @Override
 public int hashCode() {
 return this.getNode().hashCode();
 }

 /*
 * (non-Javadoc)
 *
 * @see jakarta.el.ValueExpression#isLiteralText()
 */
 @Override
 public boolean isLiteralText() {
 try {
 return this.getNode() instanceof AstLiteralExpression;
 } catch (ELException ele) {
 return false;
 }
 }

 /*
 * (non-Javadoc)
 *
 * @see jakarta.el.ValueExpression#isReadOnly(jakarta.el.ELContext)
 */
 @Override
 public boolean isReadOnly(ELContext context)
 throws PropertyNotFoundException, ELException {
 EvaluationContext ctx = new EvaluationContext(context, this.fnMapper,
 this.varMapper);
 context.notifyBeforeEvaluation(getExpressionString());
 boolean result = this.getNode().isReadOnly(ctx);
 context.notifyAfterEvaluation(getExpressionString());
 return result;
 }

 @Override
 public void readExternal(ObjectInput in) throws IOException,
 ClassNotFoundException {
 this.expr = in.readUTF();
 String type = in.readUTF();
 if (!type.isEmpty()) {
 this.expectedType = ReflectionUtil.forName(type);
 }
 this.fnMapper = (FunctionMapper) in.readObject();
 this.varMapper = (VariableMapper) in.readObject();
 }

 /*
 * (non-Javadoc)
 *
 * @see jakarta.el.ValueExpression#setValue(jakarta.el.ELContext,
 * java.lang.Object)
 */
 @Override
 public void setValue(ELContext context, Object value)
 throws PropertyNotFoundException, PropertyNotWritableException,
 ELException {
 EvaluationContext ctx = new EvaluationContext(context, this.fnMapper,
 this.varMapper);
 context.notifyBeforeEvaluation(getExpressionString());
 this.getNode().setValue(ctx, value);
 context.notifyAfterEvaluation(getExpressionString());
 }

 @Override
 public void writeExternal(ObjectOutput out) throws IOException {
 out.writeUTF(this.expr);
 out.writeUTF((this.expectedType != null) ? this.expectedType.getName()
 : "");
 out.writeObject(this.fnMapper);
 out.writeObject(this.varMapper);
 }

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

 /**
 * @since EL 2.2
 */
 @Override
 public ValueReference getValueReference(ELContext context) {
 EvaluationContext ctx = new EvaluationContext(context, this.fnMapper,
 this.varMapper);
 context.notifyBeforeEvaluation(getExpressionString());
 ValueReference result = this.getNode().getValueReference(ctx);
 context.notifyAfterEvaluation(getExpressionString());
 return result;
 }
}

quality91%

¤ Dauer der Verarbeitung: 0.22 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.