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A collection of Java utilities.
//
// $Id$
//
// samskivert library - useful routines for java programs
// Copyright (C) 2001-2010 Michael Bayne, et al.
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published
// by the Free Software Foundation; either version 2.1 of the License, or
// (at your option) any later version.
//
// This library 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 library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package com.samskivert.jdbc;
import java.io.UnsupportedEncodingException;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import com.samskivert.io.PersistenceException;
import com.samskivert.util.StringUtil;
import static com.samskivert.Log.log;
/**
* A repository for JDBC related utility functions.
*/
public class JDBCUtil
{
/** Used for {@link #batchQuery}. */
public interface BatchProcessor
{
/**
* Called for each row returned during our batch query. Do not advance the result set,
* simply query its values with the get methods.
*/
public void process (ResultSet row)
throws SQLException;
}
/**
* Closes the supplied JDBC statement and gracefully handles being passed null (by doing
* nothing).
*/
public static void close (Statement stmt)
throws SQLException
{
if (stmt != null) {
stmt.close();
}
}
/**
* Closes the supplied JDBC connection and gracefully handles being passed null (by doing
* nothing).
*/
public static void close (Connection conn)
throws SQLException
{
if (conn != null) {
conn.close();
}
}
/**
* Wraps the given connection in a proxied instance that will add all statements returned by
* methods called on the proxy (such as {@link Connection#createStatement}) to the supplied
* list. Thus you can create the proxy, pass the proxy to code that creates and uses statements
* and then close any statements created by the code that operated on that Connection before
* returning it to a pool, for example.
*/
public static Connection makeCollector (final Connection conn, final List stmts)
{
return (Connection)Proxy.newProxyInstance(
Connection.class.getClassLoader(), PROXY_IFACES, new InvocationHandler() {
public Object invoke (Object proxy, Method method, Object[] args) throws Throwable {
Object result = method.invoke(conn, args);
if (result instanceof Statement) {
stmts.add((Statement)result);
}
return result;
}
});
}
/**
* Calls stmt.executeUpdate() on the supplied statement, checking to see that it
* returns the expected update count and throwing a persistence exception if it does not.
*/
public static void checkedUpdate (PreparedStatement stmt, int expectedCount)
throws SQLException, PersistenceException
{
int modified = stmt.executeUpdate();
if (modified != expectedCount) {
String err = "Statement did not modify expected number of rows [stmt=" + stmt +
", expected=" + expectedCount + ", modified=" + modified + "]";
throw new PersistenceException(err);
}
}
/**
* Calls stmt.executeUpdate() on the supplied statement with the supplied query,
* checking to see that it returns the expected update count and throwing a persistence
* exception if it does not.
*/
public static void checkedUpdate (
Statement stmt, String query, int expectedCount)
throws SQLException, PersistenceException
{
int modified = stmt.executeUpdate(query);
if (modified != expectedCount) {
String err = "Statement did not modify expected number of rows [stmt=" + stmt +
", expected=" + expectedCount + ", modified=" + modified + "]";
throw new PersistenceException(err);
}
}
/**
* Calls stmt.executeUpdate() on the supplied statement, checking to see that it
* returns the expected update count and logging a warning if it does not.
*/
public static void warnedUpdate (PreparedStatement stmt, int expectedCount)
throws SQLException
{
int modified = stmt.executeUpdate();
if (modified != expectedCount) {
log.warning("Statement did not modify expected number of rows", "stmt", stmt,
"expected", expectedCount, "modified", modified);
}
}
/**
* Issues a query with a potentially large number of keys in batches. For example, you might
* have 10,000 ids that you wish to use in an "in" clause, but don't trust the database to be
* smart about optimizing that many keys, so instead you use batchQuery like so:
*
* Collection keys = ...;
* String query = "select NAME from USERS where USER_ID in (#KEYS)";
* JDBCUtil.BatchProcessor proc = new JDBCUtil.BatchProcessor() {
* public void process (ResultSet row) {
* String name = rs.getString(1);
* // do whatever with name
* }
* };
* JDBCUtil.batchQuery(conn, query, keys, false, 500, proc);
*
*
* @param query the SQL query to run for each batch with the string #KEYS# in the
* place where the batch of keys should be substituted.
* @param escapeKeys if true, {@link #escape} will be called on each key to escape any
* dangerous characters and wrap the key in quotes.
* @param batchSize the number of keys at a time to substitute in for #KEYS#.
*/
public static void batchQuery (Connection conn, String query, Collection keys,
boolean escapeKeys, int batchSize, BatchProcessor processor)
throws SQLException
{
Statement stmt = conn.createStatement();
try {
Iterator itr = keys.iterator();
while (itr.hasNext()) {
// group one batch of keys together
StringBuilder buf = new StringBuilder();
for (int ii = 0; ii < batchSize && itr.hasNext(); ii++) {
if (ii > 0) {
buf.append(",");
}
String key = String.valueOf(itr.next());
buf.append(escapeKeys ? escape(key) : key);
}
// issue the query with that batch
String squery = query.replace("#KEYS#", buf.toString());
ResultSet rs = stmt.executeQuery(squery);
while (rs.next()) {
processor.process(rs);
}
}
} finally {
close(stmt);
}
}
/**
* Calls stmt.executeUpdate() on the supplied statement with the supplied query,
* checking to see that it returns the expected update count and logging a warning if it does
* not.
*/
public static void warnedUpdate (
Statement stmt, String query, int expectedCount)
throws SQLException
{
int modified = stmt.executeUpdate(query);
if (modified != expectedCount) {
log.warning("Statement did not modify expected number of rows", "stmt", stmt,
"expected", expectedCount, "modified", modified);
}
}
/**
* Escapes any single quotes in the supplied text and wraps it in single quotes to make it safe
* for embedding into a database query.
*/
public static String escape (String text)
{
text = text.replace("\\", "\\\\");
return "'" + text.replace("'", "\\'") + "'";
}
/**
* Escapes a list of values, separating the escaped values by commas. See {@link
* #escape(String)}.
*/
public static String escape (Object[] values)
{
StringBuilder buf = new StringBuilder();
for (int ii = 0; ii < values.length; ii++) {
if (ii > 0) {
buf.append(", ");
}
buf.append(escape(String.valueOf(values[ii])));
}
return buf.toString();
}
/**
* Many databases simply fail to handle Unicode text properly and this routine provides a
* common workaround which is to represent a UTF-8 string as an ISO-8859-1 string. If you don't
* need to use the database's collation routines, this allows you to do pretty much exactly
* what you want at the expense of having to jigger and dejigger every goddamned string that
* might contain multibyte characters every time you access the database. Three cheers for
* progress!
*/
public static String jigger (String text)
{
if (text == null) {
return null;
}
try {
return new String(text.getBytes("UTF8"), "8859_1");
} catch (UnsupportedEncodingException uee) {
log.warning("Jigger failed", uee);
return text;
}
}
/**
* Reverses {@link #jigger}.
*/
public static String unjigger (String text)
{
if (text == null) {
return null;
}
try {
return new String(text.getBytes("8859_1"), "UTF8");
} catch (UnsupportedEncodingException uee) {
log.warning("Unjigger failed", uee);
return text;
}
}
/**
* Utility method to jigger the specified string so that it's safe to use in a regular
* Statement.
*/
public static String safeJigger (String text)
{
return jigger(text).replace("'", "\\'");
}
/**
* Used to programatically create a database table. Does nothing if the table already exists.
*
* @return true if the table was created, false if it already existed.
*/
public static boolean createTableIfMissing (
Connection conn, String table, String[] definition, String postamble)
throws SQLException
{
if (tableExists(conn, table)) {
return false;
}
Statement stmt = conn.createStatement();
try {
stmt.executeUpdate("create table " + table +
"(" + StringUtil.join(definition, ", ") + ") " + postamble);
} finally {
close(stmt);
}
log.info("Database table '" + table + "' created.");
return true;
}
/**
* Returns true if the table with the specified name exists, false if it does
* not. Note: the table name is case sensitive.
*/
public static boolean tableExists (Connection conn, String name)
throws SQLException
{
boolean matched = false;
ResultSet rs = conn.getMetaData().getTables("", "", name, null);
while (rs.next()) {
String tname = rs.getString("TABLE_NAME");
if (name.equals(tname)) {
matched = true;
}
}
return matched;
}
/**
* Returns true if the table with the specified name exists and contains a column with the
* specified name, false if either condition does not hold true. Note: the names are
* case sensitive.
*/
public static boolean tableContainsColumn (Connection conn, String table, String column)
throws SQLException
{
boolean matched = false;
ResultSet rs = conn.getMetaData().getColumns("", "", table, column);
while (rs.next()) {
String tname = rs.getString("TABLE_NAME");
String cname = rs.getString("COLUMN_NAME");
if (tname.equals(table) && cname.equals(column)) {
matched = true;
}
}
return matched;
}
/**
* Returns true if the index on the specified column exists for the specified table, false if
* it does not. Optionally you can specifiy a non null index name, and the table will be
* checked to see if it contains that specifically named index. Note: the names are
* case sensitive.
*/
public static boolean tableContainsIndex (
Connection conn, String table, String column, String index)
throws SQLException
{
boolean matched = false;
ResultSet rs = conn.getMetaData().getIndexInfo("", "", table, false, true);
while (rs.next()) {
String tname = rs.getString("TABLE_NAME");
String cname = rs.getString("COLUMN_NAME");
String iname = rs.getString("INDEX_NAME");
if (index == null) {
if (tname.equals(table) && cname.equals(column)) {
matched = true;
}
} else if (index.equals(iname)) {
matched = true;
}
}
return matched;
}
/**
* Returns true if the specified table contains a primary key on the specified column.
*/
public static boolean tableContainsPrimaryKey (Connection conn, String table, String column)
throws SQLException
{
boolean matched = false;
ResultSet rs = conn.getMetaData().getPrimaryKeys("", "", table);
while (rs.next()) {
String tname = rs.getString("TABLE_NAME");
String cname = rs.getString("COLUMN_NAME");
if (tname.equals(table) && cname.equals(column)) {
matched = true;
}
}
return matched;
}
/**
* Returns the name of the index for the specified column in the specified table.
*/
public static String getIndexName (Connection conn, String table,
String column)
throws SQLException
{
ResultSet rs = conn.getMetaData().getIndexInfo("", "", table, false, true);
while (rs.next()) {
String tname = rs.getString("TABLE_NAME");
String cname = rs.getString("COLUMN_NAME");
String iname = rs.getString("INDEX_NAME");
if (tname.equals(table) && cname.equals(column)) {
return iname;
}
}
return null;
}
/**
* Returns the type (as specified in {@link java.sql.Types} for the specified column in the
* specified table.
*/
public static int getColumnType (Connection conn, String table,
String column)
throws SQLException
{
ResultSet rs = getColumnMetaData(conn, table, column);
try {
return rs.getInt("DATA_TYPE");
} finally {
rs.close();
}
}
/**
* Determines whether or not the specified column accepts null values.
*
* @return true if the column accepts null values, false if it does not (or its nullability is
* unknown)
*/
public static boolean isColumnNullable (Connection conn, String table,
String column)
throws SQLException
{
ResultSet rs = getColumnMetaData(conn, table, column);
try {
return rs.getString("IS_NULLABLE").equals("YES");
} finally {
rs.close();
}
}
/**
* Returns the size for the specified column in the specified table. For char or date types
* this is the maximum number of characters, for numeric or decimal types this is the
* precision.
*/
public static int getColumnSize (Connection conn, String table, String column)
throws SQLException
{
ResultSet rs = getColumnMetaData(conn, table, column);
try {
return rs.getInt("COLUMN_SIZE");
} finally {
rs.close();
}
}
/**
* Returns a string representation of the default value for the specified column in the
* specified table. This may be null.
*/
public static String getColumnDefaultValue (Connection conn, String table, String column)
throws SQLException
{
ResultSet rs = getColumnMetaData(conn, table, column);
try {
return rs.getString("COLUMN_DEF");
} finally {
rs.close();
}
}
/**
* Adds a column (with name 'cname' and definition 'cdef') to the specified table.
*
* @param afterCname (optional) the name of the column after which to add the new column.
*
* @return true if the column was added, false if it already existed.
*/
public static boolean addColumn (
Connection conn, String table, String cname, String cdef, String afterCname)
throws SQLException
{
if (tableContainsColumn(conn, table, cname)) {
// Log.info("Database table '" + table + "' already has column '" + cname + "'.");
return false;
}
String update = "ALTER TABLE " + table + " ADD COLUMN " + cname + " " + cdef;
if (afterCname != null) {
update += " AFTER " + afterCname;
}
PreparedStatement stmt = null;
try {
stmt = conn.prepareStatement(update);
stmt.executeUpdate();
} finally {
close(stmt);
}
log.info("Database column '" + cname + "' added to table '" + table + "'.");
return true;
}
/**
* Changes a column's definition. Takes a full column definition 'cdef' (including the name of
* the column) with which to replace the specified column 'cname'.
*
* NOTE: A handy thing you can do with this is to rename a column by providing a column
* definition that has a different name, but the same column type.
*/
public static void changeColumn (Connection conn, String table, String cname, String cdef)
throws SQLException
{
String update = "ALTER TABLE " + table + " CHANGE " + cname + " " + cdef;
PreparedStatement stmt = null;
try {
stmt = conn.prepareStatement(update);
stmt.executeUpdate();
} finally {
close(stmt);
}
log.info("Database column '" + cname + "' of table '" + table +
"' modified to have this def '" + cdef + "'.");
}
/**
* Removes a column from the specified table.
*
* @return true if the column was dropped, false if it did not exist in the first place.
*/
public static boolean dropColumn (Connection conn, String table, String cname)
throws SQLException
{
if (!tableContainsColumn(conn, table, cname)) {
return false;
}
String update = "ALTER TABLE " + table + " DROP COLUMN " + cname;
PreparedStatement stmt = null;
try {
stmt = conn.prepareStatement(update);
if (stmt.executeUpdate() == 1) {
log.info("Database index '" + cname + "' removed from table '" + table + "'.");
}
} finally {
close(stmt);
}
return true;
}
/**
* Removes a named index from the specified table.
*
* @return true if the index was dropped, false if it did not exist in the first place.
*/
public static boolean dropIndex (Connection conn, String table, String cname, String iname)
throws SQLException
{
if (!tableContainsIndex(conn, table, cname, iname)) {
return false;
}
String update = "ALTER TABLE " + table + " DROP INDEX " + iname;
PreparedStatement stmt = null;
try {
stmt = conn.prepareStatement(update);
if (stmt.executeUpdate() == 1) {
log.info("Database index '" + iname + "' removed from table '" + table + "'.");
}
} finally {
close(stmt);
}
return true;
}
/**
* Removes the primary key from the specified table.
*/
public static void dropPrimaryKey (Connection conn, String table)
throws SQLException
{
String update = "ALTER TABLE " + table + " DROP PRIMARY KEY";
PreparedStatement stmt = null;
try {
stmt = conn.prepareStatement(update);
if (stmt.executeUpdate() == 1) {
log.info("Database primary key removed from '" + table + "'.");
}
} finally {
close(stmt);
}
}
/**
* Adds an index on the specified column (cname) to the specified table. Optionally supply an
* index name, otherwise the index is named after the column.
*
* @return true if the index was added, false if it already existed.
*/
public static boolean addIndexToTable (
Connection conn, String table, String cname, String iname)
throws SQLException
{
if (tableContainsIndex(conn, table, cname, iname)) {
// Log.info("Database table '" + table + "' already has an index " +
// "on column '" + cname + "'" +
// (iname != null ? " named '" + iname + "'." : "."));
return false;
}
String idx_name = (iname != null ? iname : cname);
String update = "CREATE INDEX " + idx_name + " on " + table + "(" + cname + ")";
PreparedStatement stmt = null;
try {
stmt = conn.prepareStatement(update);
stmt.executeUpdate();
} finally {
close(stmt);
}
log.info("Database index '" + idx_name + "' added to table '" + table + "'");
return true;
}
/**
* Helper function for {@link #getColumnType}, etc.
*/
protected static ResultSet getColumnMetaData (Connection conn, String table, String column)
throws SQLException
{
ResultSet rs = conn.getMetaData().getColumns("", "", table, column);
while (rs.next()) {
String tname = rs.getString("TABLE_NAME");
String cname = rs.getString("COLUMN_NAME");
if (tname.equals(table) && cname.equals(column)) {
return rs;
}
}
throw new SQLException("Table or Column not defined. [table=" + table +
", col=" + column + "].");
}
/** Used by {@link #makeCollector}. */
protected static final Class[] PROXY_IFACES = { Connection.class };
}