org.activiti.engine.impl.juel.ExpressionNode Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of activiti-engine Show documentation
There is a newer version: 7.1.0.M6
/*
 * Based on JUEL 2.2.1 code, 2006-2009 Odysseus Software GmbH
 *
 * 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
 *
 *     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.activiti.engine.impl.juel;

import org.activiti.engine.impl.javax.el.ELContext;
import org.activiti.engine.impl.javax.el.MethodInfo;
import org.activiti.engine.impl.javax.el.ValueReference;

/**
 * Expression node interface. This interface provides all the methods needed for value expressions and method expressions.
 * 
 * @see org.activiti.engine.impl.juel.Tree
 * @author Christoph Beck
 */
public interface ExpressionNode extends Node {
  /**
   * @return true if this node represents literal text
   */
  public boolean isLiteralText();

  /**
   * @return true if the subtree rooted at this node could be used as an lvalue expression (identifier or property sequence with non-literal prefix).
   */
  public boolean isLeftValue();

  /**
   * @return true if the subtree rooted at this node is a method invocation.
   */
  public boolean isMethodInvocation();

  /**
   * Evaluate node.
   * 
   * @param bindings
   *          bindings containing variables and functions
   * @param context
   *          evaluation context
   * @param expectedType
   *          result type
   * @return evaluated node, coerced to the expected type
   */
  public Object getValue(Bindings bindings, ELContext context, Class expectedType);

  /**
   * Get value reference.
   * 
   * @param bindings
   * @param context
   * @return value reference
   */
  public ValueReference getValueReference(Bindings bindings, ELContext context);

  /**
   * Get the value type accepted in {@link #setValue(Bindings, ELContext, Object)}.
   * 
   * @param bindings
   *          bindings containing variables and functions
   * @param context
   *          evaluation context
   * @return accepted type or null for non-lvalue nodes
   */
  public Class getType(Bindings bindings, ELContext context);

  /**
   * Determine whether {@link #setValue(Bindings, ELContext, Object)} will throw a {@link org.activiti.engine.impl.javax.el.PropertyNotWritableException}.
   * 
   * @param bindings
   *          bindings containing variables and functions
   * @param context
   *          evaluation context
   * @return true if this a read-only expression node
   */
  public boolean isReadOnly(Bindings bindings, ELContext context);

  /**
   * Assign value.
   * 
   * @param bindings
   *          bindings containing variables and functions
   * @param context
   *          evaluation context
   * @param value
   *          value to set
   */
  public void setValue(Bindings bindings, ELContext context, Object value);

  /**
   * Get method information. If this is a non-lvalue node, answer null.
   * 
   * @param bindings
   *          bindings containing variables and functions
   * @param context
   *          evaluation context
   * @param returnType
   *          expected method return type (may be null meaning don't care)
   * @param paramTypes
   *          expected method argument types
   * @return method information or null
   */
  public MethodInfo getMethodInfo(Bindings bindings, ELContext context, Class returnType, Class[] paramTypes);

  /**
   * Invoke method.
   * 
   * @param bindings
   *          bindings containing variables and functions
   * @param context
   *          evaluation context
   * @param returnType
   *          expected method return type (may be null meaning don't care)
   * @param paramTypes
   *          expected method argument types
   * @param paramValues
   *          parameter values
   * @return result of the method invocation
   */
  public Object invoke(Bindings bindings, ELContext context, Class returnType, Class[] paramTypes, Object[] paramValues);

  /**
   * Get the canonical expression string for this node. Variable and function names will be replaced in a way such that two expression nodes that have the same node structure and bindings will also
   * answer the same value here.
   * 
   * For example, "${foo:bar()+2*foobar}" may lead to "${<fn>() + 2 * <var>}" if foobar is a bound variable. Otherwise, the structural id would be
   * "${<fn>() + 2 * foobar}".
   * 
   * If the bindings is null, the full canonical subexpression is returned.
   */
  public String getStructuralId(Bindings bindings);
}