java/engine/org/apache/derby/impl/sql/compile/StaticClassFieldReferenceNode.java

/*

   Derby - Class org.apache.derby.impl.sql.compile.StaticClassFieldReferenceNode

   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.derby.impl.sql.compile;

import java.lang.reflect.Member;
import java.lang.reflect.Modifier;
import java.util.List;
import org.apache.derby.iapi.error.StandardException;
import org.apache.derby.iapi.reference.SQLState;
import org.apache.derby.iapi.services.compiler.MethodBuilder;
import org.apache.derby.iapi.services.context.ContextManager;
import org.apache.derby.iapi.services.loader.ClassInspector;
import org.apache.derby.shared.common.sanity.SanityManager;
import org.apache.derby.iapi.sql.compile.CompilerContext;
import org.apache.derby.iapi.store.access.Qualifier;
import org.apache.derby.iapi.util.JBitSet;

/**
 * A StaticClassFieldReferenceNode represents a Java static field reference from 
 * a Class (as opposed to an Object).  Field references can be 
 * made in DML (as expressions).
 *
 */

public final class StaticClassFieldReferenceNode extends JavaValueNode
{
	/*
	** Name of the field.
	*/
	private String	fieldName;

	/* The class name */
	private String	javaClassName;
	private boolean classNameDelimitedIdentifier;

	/**
		The field we are going to access.
	*/
	private Member			field;

	/**
     * Constructor for a StaticClassFieldReferenceNode
	 *
	 * @param	javaClassName	The class name
	 * @param	fieldName		The field name
     * @param   cm              The context manager
	 */
    StaticClassFieldReferenceNode(
            String javaClassName,
            String fieldName,
            boolean classNameDelimitedIdentifier,
            ContextManager cm)
	{
        super(cm);
        this.fieldName = fieldName;
        this.javaClassName = javaClassName;
        this.classNameDelimitedIdentifier = classNameDelimitedIdentifier;
	}

	/**
	 * Bind this expression.  This means binding the sub-expressions,
	 * as well as figuring out what the return type is for this expression.
	 *
	 * @param fromList		The FROM list for the query this
     *                      expression is in, for binding columns.
     * @param subqueryList  The subquery list being built as we find SubqueryNodes
     * @param aggregates    The aggregate list being built as we find AggregateNodes
	 *
	 * @return	Nothing
	 *
	 * @exception StandardException		Thrown on error
	 */
    JavaValueNode bindExpression(FromList fromList,
                                 SubqueryList subqueryList,
                                 List<AggregateNode> aggregates)
			throws StandardException
	{
		ClassInspector classInspector = getClassFactory().getClassInspector();


		if (((getCompilerContext().getReliability() & CompilerContext.INTERNAL_SQL_ILLEGAL) != 0)
			|| !javaClassName.startsWith("java.sql.")) {

			throw StandardException.newException(SQLState.LANG_SYNTAX_ERROR, javaClassName + "::" + fieldName);
		}

		verifyClassExist(javaClassName);

		/*
		** Find the field that is public.
		*/
		field = classInspector.findPublicField(javaClassName,
										fieldName,
										true);
		/* Get the field type */
	 	setJavaTypeName( classInspector.getType(field) );

		return this;

	}

	/**
	 * Preprocess an expression tree.  We do a number of transformations
	 * here (including subqueries, IN lists, LIKE and BETWEEN) plus
	 * subquery flattening.
	 * NOTE: This is done before the outer ResultSetNode is preprocessed.
	 *
	 * @param	numTables			Number of tables in the DML Statement
	 * @param	outerFromList		FromList from outer query block
	 * @param	outerSubqueryList	SubqueryList from outer query block
	 * @param	outerPredicateList	PredicateList from outer query block
	 *
	 * @exception StandardException		Thrown on error
	 */
    void preprocess(int numTables,
							FromList outerFromList,
							SubqueryList outerSubqueryList,
							PredicateList outerPredicateList) 
					throws StandardException
	{
	}

	/**
	 * Categorize this predicate.  Initially, this means
	 * building a bit map of the referenced tables for each predicate.
	 * If the source of this ColumnReference (at the next underlying level) 
	 * is not a ColumnReference or a VirtualColumnNode then this predicate
	 * will not be pushed down.
	 *
	 * For example, in:
	 *		select * from (select 1 from s) a (x) where x = 1
	 * we will not push down x = 1.
	 * NOTE: It would be easy to handle the case of a constant, but if the
	 * inner SELECT returns an arbitrary expression, then we would have to copy
	 * that tree into the pushed predicate, and that tree could contain
	 * subqueries and method calls.
	 * RESOLVE - revisit this issue once we have views.
	 *
	 * @param referencedTabs	JBitSet with bit map of referenced FromTables
	 * @param simplePredsOnly	Whether or not to consider method
	 *							calls, field references and conditional nodes
	 *							when building bit map
	 *
	 * @return boolean		Whether or not source.expression is a ColumnReference
	 *						or a VirtualColumnNode.
	 */
    boolean categorize(JBitSet referencedTabs, boolean simplePredsOnly)
	{
		return true;
	}

	/**
	 * Remap all ColumnReferences in this tree to be clones of the
	 * underlying expression.
	 *
	 * @return JavaValueNode			The remapped expression tree.
	 *
	 * @exception StandardException			Thrown on error
	 */
    JavaValueNode remapColumnReferencesToExpressions()
		throws StandardException
	{
		return this;
	}

	/**
	 * Return the variant type for the underlying expression.
	 * The variant type can be:
	 *		VARIANT				- variant within a scan
	 *							  (method calls and non-static field access)
	 *		SCAN_INVARIANT		- invariant within a scan
	 *							  (column references from outer tables)
	 *		QUERY_INVARIANT		- invariant within the life of a query
	 *		CONSTANT			- constant
	 *
	 * @return	The variant type for the underlying expression.
	 */
    @Override
    int getOrderableVariantType()
	{
		if (SanityManager.DEBUG)
		{
			SanityManager.ASSERT(field != null,
					"field is expected to be non-null");
		}
		/* Static field references are invariant for the life 
		 * of the query, non-static are variant.
		 */
		if (Modifier.isFinal(field.getModifiers()))
		{
			return Qualifier.CONSTANT;
		}
		else
		{
			return Qualifier.VARIANT;
		}
	}

	/**
	 * @see QueryTreeNode#generate
	 *
	 * @exception StandardException		Thrown on error
	 */
    void generateExpression(ExpressionClassBuilder acb, MethodBuilder mb)
	throws StandardException
	{
		/*
		** Generate the following:
		**
		** <javaClassName>.<field name>
		*/

		mb.getStaticField(field.getDeclaringClass().getName(),
								 fieldName,
								 getJavaTypeName());
	}

}