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<html><head><META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Appendix B. First JDBC Client Example</title><link href="guide.css" rel="stylesheet" type="text/css"><meta content="DocBook XSL Stylesheets V1.65.1" name="generator"><meta name="keywords" content="Hsqldb, Hypersonic, Database, JDBC, Java"><link rel="home" href="index.html" title="Hsqldb User Guide"><link rel="up" href="index.html" title="Hsqldb User Guide"><link rel="previous" href="apa.html" title="Appendix A. Building HSQLDB"><link rel="next" href="apc.html" title="Appendix C. Hsqldb Database Files and Recovery"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table summary="Navigation header" width="100%"><tr><th align="center" colspan="3">Appendix B. First JDBC Client Example</th></tr><tr><td align="left" width="20%"><a accesskey="p" href="apa.html"><img src="navicons/prev.gif" alt="Prev"></a> </td><th align="center" width="60%"> </th><td align="right" width="20%"> <a accesskey="n" href="apc.html"><img src="navicons/next.gif" alt="Next"></a></td></tr></table><hr></div><div class="appendix" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="firstclient-appendix"></a>Appendix B. First JDBC Client Example</h2></div></div><div></div></div><p>
There is a copy of <tt class="filename">Testdb.java</tt> in the
directory <tt class="filename">src/org/hsqldb/sample</tt> of your
HSQLDB distribution.
</p><div class="example"><a name="N1280A"></a><p class="title"><b>Example B.1. JDBC Client source code example</b></p><pre class="programlisting">/* Copyright (c) 2001-2005, The HSQL Development Group
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* Neither the name of the HSQL Development Group nor the names of its
* contributors may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.hsqldb.sample;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
/**
* Title: Testdb
* Description: simple hello world db example of a
* standalone persistent db application
*
* every time it runs it adds four more rows to sample_table
* it does a query and prints the results to standard out
*
* Author: Karl Meissner karl@meissnersd.com
*/
public class Testdb {
Connection conn; //our connnection to the db - presist for life of program
// we dont want this garbage collected until we are done
public Testdb(String db_file_name_prefix) throws Exception { // note more general exception
// Load the HSQL Database Engine JDBC driver
// hsqldb.jar should be in the class path or made part of the current jar
Class.forName("org.hsqldb.jdbcDriver");
// connect to the database. This will load the db files and start the
// database if it is not alread running.
// db_file_name_prefix is used to open or create files that hold the state
// of the db.
// It can contain directory names relative to the
// current working directory
conn = DriverManager.getConnection("jdbc:hsqldb:"
+ db_file_name_prefix, // filenames
"sa", // username
""); // password
}
public void shutdown() throws SQLException {
Statement st = conn.createStatement();
// db writes out to files and performs clean shuts down
// otherwise there will be an unclean shutdown
// when program ends
st.execute("SHUTDOWN");
conn.close(); // if there are no other open connection
}
//use for SQL command SELECT
public synchronized void query(String expression) throws SQLException {
Statement st = null;
ResultSet rs = null;
st = conn.createStatement(); // statement objects can be reused with
// repeated calls to execute but we
// choose to make a new one each time
rs = st.executeQuery(expression); // run the query
// do something with the result set.
dump(rs);
st.close(); // NOTE!! if you close a statement the associated ResultSet is
// closed too
// so you should copy the contents to some other object.
// the result set is invalidated also if you recycle an Statement
// and try to execute some other query before the result set has been
// completely examined.
}
//use for SQL commands CREATE, DROP, INSERT and UPDATE
public synchronized void update(String expression) throws SQLException {
Statement st = null;
st = conn.createStatement(); // statements
int i = st.executeUpdate(expression); // run the query
if (i == -1) {
System.out.println("db error : " + expression);
}
st.close();
} // void update()
public static void dump(ResultSet rs) throws SQLException {
// the order of the rows in a cursor
// are implementation dependent unless you use the SQL ORDER statement
ResultSetMetaData meta = rs.getMetaData();
int colmax = meta.getColumnCount();
int i;
Object o = null;
// the result set is a cursor into the data. You can only
// point to one row at a time
// assume we are pointing to BEFORE the first row
// rs.next() points to next row and returns true
// or false if there is no next row, which breaks the loop
for (; rs.next(); ) {
for (i = 0; i < colmax; ++i) {
o = rs.getObject(i + 1); // Is SQL the first column is indexed
// with 1 not 0
System.out.print(o.toString() + " ");
}
System.out.println(" ");
}
} //void dump( ResultSet rs )
public static void main(String[] args) {
Testdb db = null;
try {
db = new Testdb("db_file");
} catch (Exception ex1) {
ex1.printStackTrace(); // could not start db
return; // bye bye
}
try {
//make an empty table
//
// by declaring the id column IDENTITY, the db will automatically
// generate unique values for new rows- useful for row keys
db.update(
"CREATE TABLE sample_table ( id INTEGER IDENTITY, str_col VARCHAR(256), num_col INTEGER)");
} catch (SQLException ex2) {
//ignore
//ex2.printStackTrace(); // second time we run program
// should throw execption since table
// already there
//
// this will have no effect on the db
}
try {
// add some rows - will create duplicates if run more then once
// the id column is automatically generated
db.update(
"INSERT INTO sample_table(str_col,num_col) VALUES('Ford', 100)");
db.update(
"INSERT INTO sample_table(str_col,num_col) VALUES('Toyota', 200)");
db.update(
"INSERT INTO sample_table(str_col,num_col) VALUES('Honda', 300)");
db.update(
"INSERT INTO sample_table(str_col,num_col) VALUES('GM', 400)");
// do a query
db.query("SELECT * FROM sample_table WHERE num_col < 250");
// at end of program
db.shutdown();
} catch (SQLException ex3) {
ex3.printStackTrace();
}
} // main()
} // class Testdb
</pre></div></div><div class="navfooter"><hr><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="apa.html"><img src="navicons/prev.gif" alt="Prev"></a> </td><td align="center" width="20%"><a accesskey="u" href="index.html"><img src="navicons/up.gif" alt="Up"></a></td><td align="right" width="40%"> <a accesskey="n" href="apc.html"><img src="navicons/next.gif" alt="Next"></a></td></tr><tr><td valign="top" align="left" width="40%">Appendix A. Building HSQLDB </td><td align="center" width="20%"><a accesskey="h" href="index.html"><img src="navicons/home.gif" alt="Home"></a></td><td valign="top" align="right" width="40%"> Appendix C. Hsqldb Database Files and Recovery</td></tr></table></div></body></html>
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