Hibernate example source code file (ClobProxy.java)

This example Hibernate source code file (ClobProxy.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Hibernate tags/keywords

classloader, clob, clob, clobproxy, clobproxy, integer, io, jdbc, object, proxy_interfaces, reader, reflection, sql, sqlexception, sqlexception, start, start, string

The Hibernate ClobProxy.java source code

/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2009 by Red Hat Inc and/or its affiliates or by
 * third-party contributors as indicated by either @author tags or express
 * copyright attribution statements applied by the authors.  All
 * third-party contributions are distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.engine.jdbc;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.io.StringReader;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Clob;
import java.sql.SQLException;

import org.hibernate.type.descriptor.java.DataHelper;

/**
 * Manages aspects of proxying {@link Clob Clobs} for non-contextual creation, including proxy creation and
 * handling proxy invocations.
 *
 * @author Gavin King
 * @author Steve Ebersole
 * @author Gail Badner
 */
public class ClobProxy implements InvocationHandler {
	private static final Class[] PROXY_INTERFACES = new Class[] { Clob.class, ClobImplementer.class };

	private String string;
	private Reader reader;
	private long length;
	private boolean needsReset = false;


	/**
	 * Constructor used to build {@link Clob} from string data.
	 *
	 * @param string The byte array
	 * @see #generateProxy(String)
	 */
	protected ClobProxy(String string) {
		this.string = string;
		reader = new StringReader(string);
		length = string.length();
	}

	/**
	 * Constructor used to build {@link Clob} from a reader.
	 *
	 * @param reader The character reader.
	 * @param length The length of the reader stream.
	 * @see #generateProxy(java.io.Reader, long)
	 */
	protected ClobProxy(Reader reader, long length) {
		this.reader = reader;
		this.length = length;
	}

	protected long getLength() {
		return length;
	}

	protected InputStream getAsciiStream() throws SQLException {
		resetIfNeeded();
		return new ReaderInputStream( reader );
	}

	protected Reader getCharacterStream() throws SQLException {
		resetIfNeeded();
		return reader;
	}

	protected String getSubString(long start, int length) {
		if ( string == null ) {
			throw new UnsupportedOperationException( "Clob was not created from string; cannot substring" );
		}
		// semi-naive implementation
		int endIndex = Math.min( ((int)start)+length, string.length() );
		return string.substring( (int)start, endIndex );
	}

	/**
	 * {@inheritDoc}
	 *
	 * @throws UnsupportedOperationException if any methods other than {@link Clob#length()},
	 * {@link Clob#getAsciiStream()}, or {@link Clob#getCharacterStream()} are invoked.
	 */
	@SuppressWarnings({ "UnnecessaryBoxing" })
	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
		final String methodName = method.getName();
		final int argCount = method.getParameterTypes().length;

		if ( "length".equals( methodName ) && argCount == 0 ) {
			return Long.valueOf( getLength() );
		}
		if ( "getAsciiStream".equals( methodName ) && argCount == 0 ) {
			return getAsciiStream();
		}
		if ( "getCharacterStream".equals( methodName ) ) {
			if ( argCount == 0 ) {
				return getCharacterStream();
			}
			else if ( argCount == 2 ) {
				long start = (Long) args[0];
				if ( start < 1 ) {
					throw new SQLException( "Start position 1-based; must be 1 or more." );
				}
				if ( start > getLength() ) {
					throw new SQLException( "Start position [" + start + "] cannot exceed overall CLOB length [" + getLength() + "]" );
				}
				int length = (Integer) args[1];
				if ( length < 0 ) {
					// java docs specifically say for getCharacterStream(long,int) that the start+length must not exceed the
					// total length, however that is at odds with the getSubString(long,int) behavior.
					throw new SQLException( "Length must be great-than-or-equal to zero." );
				}
				return DataHelper.subStream( getCharacterStream(), start-1, length );
			}
		}
		if ( "getSubString".equals( methodName ) && argCount == 2 ) {
			long start = (Long) args[0];
			if ( start < 1 ) {
				throw new SQLException( "Start position 1-based; must be 1 or more." );
			}
			if ( start > getLength() ) {
				throw new SQLException( "Start position [" + start + "] cannot exceed overall CLOB length [" + getLength() + "]" );
			}
			int length = (Integer) args[1];
			if ( length < 0 ) {
				throw new SQLException( "Length must be great-than-or-equal to zero." );
			}
			return getSubString( start-1, length );
		}
		if ( "free".equals( methodName ) && argCount == 0 ) {
			reader.close();
			return null;
		}
		if ( "toString".equals( methodName ) && argCount == 0 ) {
			return this.toString();
		}
		if ( "equals".equals( methodName ) && argCount == 1 ) {
			return Boolean.valueOf( proxy == args[0] );
		}
		if ( "hashCode".equals( methodName ) && argCount == 0 ) {
			return new Integer( this.hashCode() );
		}

		throw new UnsupportedOperationException( "Clob may not be manipulated from creating session" );
	}

	protected void resetIfNeeded() throws SQLException {
		try {
			if ( needsReset ) {
				reader.reset();
			}
		}
		catch ( IOException ioe ) {
			throw new SQLException( "could not reset reader", ioe );
		}
		needsReset = true;
	}

	/**
	 * Generates a {@link Clob} proxy using the string data.
	 *
	 * @param string The data to be wrapped as a {@link Clob}.
	 *
	 * @return The generated proxy.
	 */
	public static Clob generateProxy(String string) {
		return ( Clob ) Proxy.newProxyInstance(
				getProxyClassLoader(),
				PROXY_INTERFACES,
				new ClobProxy( string )
		);
	}

	/**
	 * Generates a {@link Clob} proxy using a character reader of given length.
	 *
	 * @param reader The character reader
	 * @param length The length of the character reader
	 *
	 * @return The generated proxy.
	 */
	public static Clob generateProxy(Reader reader, long length) {
		return ( Clob ) Proxy.newProxyInstance(
				getProxyClassLoader(),
				PROXY_INTERFACES,
				new ClobProxy( reader, length )
		);
	}

	/**
	 * Determines the appropriate class loader to which the generated proxy
	 * should be scoped.
	 *
	 * @return The class loader appropriate for proxy construction.
	 */
	protected static ClassLoader getProxyClassLoader() {
		ClassLoader cl = Thread.currentThread().getContextClassLoader();
		if ( cl == null ) {
			cl = ClobImplementer.class.getClassLoader();
		}
		return cl;
	}
}