staticclassfieldreferencenode.java

derby database source code.good for you.

/*

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

   Copyright 1997, 2004 The Apache Software Foundation or its licensors, as applicable.

   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.apache.derby.impl.sql.compile;

import org.apache.derby.iapi.services.monitor.Monitor;

import org.apache.derby.iapi.services.compiler.MethodBuilder;

import org.apache.derby.iapi.services.sanity.SanityManager;

import org.apache.derby.iapi.error.StandardException;

import org.apache.derby.iapi.sql.dictionary.DataDictionary;
import org.apache.derby.iapi.reference.SQLState;

import org.apache.derby.iapi.services.loader.ClassInspector;

import org.apache.derby.iapi.store.access.Qualifier;

import org.apache.derby.impl.sql.compile.ExpressionClassBuilder;
import org.apache.derby.iapi.sql.compile.CompilerContext;

import org.apache.derby.iapi.util.JBitSet;

import java.lang.reflect.Member;
import java.lang.reflect.Modifier;

import java.util.Vector;

/**
 * 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).
 *
 * @author Jerry Brenner
 */

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;

	/**
	 * Initializer for a StaticClassFieldReferenceNode
	 *
	 * @param	javaClassName	The class name
	 * @param	fieldName		The field name
	 */
	public void init(Object javaClassName, Object fieldName, Object classNameDelimitedIdentifier)
	{
		this.fieldName = (String) fieldName;
		this.javaClassName = (String) javaClassName;
		this.classNameDelimitedIdentifier = ((Boolean) classNameDelimitedIdentifier).booleanValue();
	}

	/**
	 * 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 aggregateVector	The aggregate vector being built as we find AggregateNodes
	 *
	 * @return	Nothing
	 *
	 * @exception StandardException		Thrown on error
	 */

	public JavaValueNode bindExpression(FromList fromList, SubqueryList subqueryList,
		Vector aggregateVector) 
			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);
		}

		javaClassName = verifyClassExist(javaClassName, ! classNameDelimitedIdentifier);

		/*
		** 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
	 *
	 * @return	Nothing.
	 *
	 * @exception StandardException		Thrown on error
	 */
	public 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.
	 */
	public 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
	 */
	public 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.
	 */
	protected 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
	 */
	public void generateExpression(ExpressionClassBuilder acb,
											MethodBuilder mb)
	{
		/*
		** Generate the following:
		**
		** <javaClassName>.<field name>
		*/

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

}