489 lines
17 KiB
Java
489 lines
17 KiB
Java
package com.moparisthebest.jdbc;
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/*
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Derby - Class SimpleApp
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import java.sql.Connection;
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import java.sql.DriverManager;
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import java.sql.PreparedStatement;
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import java.sql.ResultSet;
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import java.sql.SQLException;
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import java.sql.Statement;
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import java.util.ArrayList;
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import java.util.Properties;
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/**
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* <p>
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* This sample program is a minimal Java application showing JDBC access to a
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* Derby database.</p>
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* <p>
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* Instructions for how to run this program are
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* given in <A HREF=example.html>example.html</A>, by default located in the
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* same directory as this source file ($DERBY_HOME/demo/programs/simple/).</p>
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* <p>
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* Derby applications can run against Derby running in an embedded
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* or a client/server framework.</p>
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* <p>
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* When Derby runs in an embedded framework, the JDBC application and Derby
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* run in the same Java Virtual Machine (JVM). The application
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* starts up the Derby engine.</p>
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* <p>
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* When Derby runs in a client/server framework, the application runs in a
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* different JVM from Derby. The application only needs to load the client
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* driver, and the connectivity framework (in this case the Derby Network
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* Server) provides network connections.</p>
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*/
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public class SimpleApp
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{
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/* the default framework is embedded*/
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private String framework = "embedded";
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private String driver = "org.apache.derby.jdbc.EmbeddedDriver";
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private String protocol = "jdbc:derby:";
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/**
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* <p>
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* Starts the demo by creating a new instance of this class and running
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* the <code>go()</code> method.</p>
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* <p>
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* When you run this application, you may give one of the following
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* arguments:
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* <ul>
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<li><code>embedded</code> - default, if none specified. Will use
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* Derby's embedded driver. This driver is included in the derby.jar
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* file.</li>
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* <li><code>derbyclient</code> - will use the Derby client driver to
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* access the Derby Network Server. This driver is included in the
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* derbyclient.jar file.</li>
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* </ul>
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* <p>
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* When you are using a client/server framework, the network server must
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* already be running when trying to obtain client connections to Derby.
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* This demo program will will try to connect to a network server on this
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* host (the localhost), see the <code>protocol</code> instance variable.
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* </p>
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* <p>
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* When running this demo, you must include the correct driver in the
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* classpath of the JVM. See <a href="example.html">example.html</a> for
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* details.
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* </p>
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* @param args This program accepts one optional argument specifying which
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* connection framework (JDBC driver) to use (see above). The default
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* is to use the embedded JDBC driver.
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*/
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public static void main(String[] args)
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{
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new SimpleApp().go(args);
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System.out.println("SimpleApp finished");
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}
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/**
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* <p>
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* Starts the actual demo activities. This includes loading the correct
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* JDBC driver, creating a database by making a connection to Derby,
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* creating a table in the database, and inserting, updating and retrieving
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* some data. Some of the retrieved data is then verified (compared) against
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* the expected results. Finally, the table is deleted and, if the embedded
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* framework is used, the database is shut down.</p>
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* <p>
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* Generally, when using a client/server framework, other clients may be
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* (or want to be) connected to the database, so you should be careful about
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* doing shutdown unless you know that no one else needs to access the
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* database until it is rebooted. That is why this demo will not shut down
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* the database unless it is running Derby embedded.</p>
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*
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* @param args - Optional argument specifying which framework or JDBC driver
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* to use to connect to Derby. Default is the embedded framework,
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* see the <code>main()</code> method for details.
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* @see #main(String[])
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*/
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void go(String[] args)
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{
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/* parse the arguments to determine which framework is desired*/
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parseArguments(args);
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System.out.println("SimpleApp starting in " + framework + " mode");
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/* load the desired JDBC driver */
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loadDriver();
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/* We will be using Statement and PreparedStatement objects for
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* executing SQL. These objects, as well as Connections and ResultSets,
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* are resources that should be released explicitly after use, hence
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* the try-catch-finally pattern used below.
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* We are storing the Statement and Prepared statement object references
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* in an array list for convenience.
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*/
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Connection conn = null;
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/* This ArrayList usage may cause a warning when compiling this class
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* with a compiler for J2SE 5.0 or newer. We are not using generics
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* because we want the source to support J2SE 1.4.2 environments. */
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ArrayList statements = new ArrayList(); // list of Statements, PreparedStatements
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PreparedStatement psInsert = null;
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PreparedStatement psUpdate = null;
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Statement s = null;
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ResultSet rs = null;
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try
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{
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Properties props = new Properties(); // connection properties
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// providing a user name and password is optional in the embedded
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// and derbyclient frameworks
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props.put("user", "user1");
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props.put("password", "user1");
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/* By default, the schema APP will be used when no username is
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* provided.
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* Otherwise, the schema name is the same as the user name (in this
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* case "user1" or USER1.)
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*
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* Note that user authentication is off by default, meaning that any
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* user can connect to your database using any password. To enable
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* authentication, see the Derby Developer's Guide.
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*/
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String dbName = "derbyDB"; // the name of the database
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/*
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* This connection specifies create=true in the connection URL to
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* cause the database to be created when connecting for the first
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* time. To remove the database, remove the directory derbyDB (the
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* same as the database name) and its contents.
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*
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* The directory derbyDB will be created under the directory that
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* the system property derby.system.home points to, or the current
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* directory (user.dir) if derby.system.home is not set.
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*/
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conn = DriverManager.getConnection(protocol + dbName
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+ ";create=true", props);
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System.out.println("Connected to and created database " + dbName);
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// We want to control transactions manually. Autocommit is on by
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// default in JDBC.
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conn.setAutoCommit(false);
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/* Creating a statement object that we can use for running various
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* SQL statements commands against the database.*/
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s = conn.createStatement();
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statements.add(s);
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// We create a table...
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s.execute("create table location(num int, addr varchar(40))");
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System.out.println("Created table location");
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// and add a few rows...
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/* It is recommended to use PreparedStatements when you are
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* repeating execution of an SQL statement. PreparedStatements also
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* allows you to parameterize variables. By using PreparedStatements
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* you may increase performance (because the Derby engine does not
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* have to recompile the SQL statement each time it is executed) and
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* improve security (because of Java type checking).
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*/
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// parameter 1 is num (int), parameter 2 is addr (varchar)
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psInsert = conn.prepareStatement(
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"insert into location values (?, ?)");
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statements.add(psInsert);
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psInsert.setInt(1, 1956);
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psInsert.setString(2, "Webster St.");
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psInsert.executeUpdate();
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System.out.println("Inserted 1956 Webster");
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psInsert.setInt(1, 1910);
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psInsert.setString(2, "Union St.");
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psInsert.executeUpdate();
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System.out.println("Inserted 1910 Union");
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// Let's update some rows as well...
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// parameter 1 and 3 are num (int), parameter 2 is addr (varchar)
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psUpdate = conn.prepareStatement(
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"update location set num=?, addr=? where num=?");
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statements.add(psUpdate);
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psUpdate.setInt(1, 180);
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psUpdate.setString(2, "Grand Ave.");
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psUpdate.setInt(3, 1956);
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psUpdate.executeUpdate();
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System.out.println("Updated 1956 Webster to 180 Grand");
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psUpdate.setInt(1, 300);
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psUpdate.setString(2, "Lakeshore Ave.");
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psUpdate.setInt(3, 180);
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psUpdate.executeUpdate();
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System.out.println("Updated 180 Grand to 300 Lakeshore");
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/*
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We select the rows and verify the results.
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*/
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rs = s.executeQuery(
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"SELECT num, addr FROM location ORDER BY num");
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/* we expect the first returned column to be an integer (num),
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* and second to be a String (addr). Rows are sorted by street
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* number (num).
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*
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* Normally, it is best to use a pattern of
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* while(rs.next()) {
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* // do something with the result set
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* }
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* to process all returned rows, but we are only expecting two rows
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* this time, and want the verification code to be easy to
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* comprehend, so we use a different pattern.
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*/
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int number; // street number retrieved from the database
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boolean failure = false;
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if (!rs.next())
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{
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failure = true;
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reportFailure("No rows in ResultSet");
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}
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if ((number = rs.getInt(1)) != 300)
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{
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failure = true;
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reportFailure(
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"Wrong row returned, expected num=300, got " + number);
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}
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if (!rs.next())
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{
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failure = true;
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reportFailure("Too few rows");
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}
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if ((number = rs.getInt(1)) != 1910)
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{
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failure = true;
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reportFailure(
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"Wrong row returned, expected num=1910, got " + number);
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}
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if (rs.next())
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{
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failure = true;
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reportFailure("Too many rows");
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}
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if (!failure) {
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System.out.println("Verified the rows");
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}
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// delete the table
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s.execute("drop table location");
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System.out.println("Dropped table location");
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/*
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We commit the transaction. Any changes will be persisted to
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the database now.
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*/
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conn.commit();
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System.out.println("Committed the transaction");
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/*
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* In embedded mode, an application should shut down the database.
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* If the application fails to shut down the database,
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* Derby will not perform a checkpoint when the JVM shuts down.
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* This means that it will take longer to boot (connect to) the
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* database the next time, because Derby needs to perform a recovery
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* operation.
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*
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* It is also possible to shut down the Derby system/engine, which
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* automatically shuts down all booted databases.
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*
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* Explicitly shutting down the database or the Derby engine with
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* the connection URL is preferred. This style of shutdown will
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* always throw an SQLException.
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*
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* Not shutting down when in a client environment, see method
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* Javadoc.
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*/
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if (framework.equals("embedded"))
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{
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try
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{
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// the shutdown=true attribute shuts down Derby
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DriverManager.getConnection("jdbc:derby:;shutdown=true");
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// To shut down a specific database only, but keep the
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// engine running (for example for connecting to other
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// databases), specify a database in the connection URL:
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//DriverManager.getConnection("jdbc:derby:" + dbName + ";shutdown=true");
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}
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catch (SQLException se)
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{
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if (( (se.getErrorCode() == 50000)
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&& ("XJ015".equals(se.getSQLState()) ))) {
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// we got the expected exception
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System.out.println("Derby shut down normally");
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// Note that for single database shutdown, the expected
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// SQL state is "08006", and the error code is 45000.
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} else {
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// if the error code or SQLState is different, we have
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// an unexpected exception (shutdown failed)
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System.err.println("Derby did not shut down normally");
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printSQLException(se);
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}
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}
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}
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}
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catch (SQLException sqle)
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{
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printSQLException(sqle);
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} finally {
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// release all open resources to avoid unnecessary memory usage
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// ResultSet
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try {
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if (rs != null) {
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rs.close();
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rs = null;
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}
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} catch (SQLException sqle) {
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printSQLException(sqle);
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}
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// Statements and PreparedStatements
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int i = 0;
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while (!statements.isEmpty()) {
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// PreparedStatement extend Statement
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Statement st = (Statement)statements.remove(i);
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try {
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if (st != null) {
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st.close();
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st = null;
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}
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} catch (SQLException sqle) {
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printSQLException(sqle);
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}
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}
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//Connection
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try {
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if (conn != null) {
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conn.close();
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conn = null;
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}
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} catch (SQLException sqle) {
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printSQLException(sqle);
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}
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}
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}
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/**
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* Loads the appropriate JDBC driver for this environment/framework. For
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* example, if we are in an embedded environment, we load Derby's
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* embedded Driver, <code>org.apache.derby.jdbc.EmbeddedDriver</code>.
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*/
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private void loadDriver() {
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/*
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* The JDBC driver is loaded by loading its class.
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* If you are using JDBC 4.0 (Java SE 6) or newer, JDBC drivers may
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* be automatically loaded, making this code optional.
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*
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* In an embedded environment, this will also start up the Derby
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* engine (though not any databases), since it is not already
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* running. In a client environment, the Derby engine is being run
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* by the network server framework.
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*
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* In an embedded environment, any static Derby system properties
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* must be set before loading the driver to take effect.
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*/
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try {
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Class.forName(driver).newInstance();
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System.out.println("Loaded the appropriate driver");
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} catch (ClassNotFoundException cnfe) {
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System.err.println("\nUnable to load the JDBC driver " + driver);
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System.err.println("Please check your CLASSPATH.");
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cnfe.printStackTrace(System.err);
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} catch (InstantiationException ie) {
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System.err.println(
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"\nUnable to instantiate the JDBC driver " + driver);
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ie.printStackTrace(System.err);
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} catch (IllegalAccessException iae) {
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System.err.println(
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"\nNot allowed to access the JDBC driver " + driver);
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iae.printStackTrace(System.err);
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}
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}
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/**
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* Reports a data verification failure to System.err with the given message.
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*
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* @param message A message describing what failed.
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*/
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private void reportFailure(String message) {
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System.err.println("\nData verification failed:");
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System.err.println('\t' + message);
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}
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/**
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* Prints details of an SQLException chain to <code>System.err</code>.
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* Details included are SQL State, Error code, Exception message.
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*
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* @param e the SQLException from which to print details.
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*/
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public static void printSQLException(SQLException e)
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{
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// Unwraps the entire exception chain to unveil the real cause of the
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// Exception.
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while (e != null)
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{
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System.err.println("\n----- SQLException -----");
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System.err.println(" SQL State: " + e.getSQLState());
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System.err.println(" Error Code: " + e.getErrorCode());
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System.err.println(" Message: " + e.getMessage());
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// for stack traces, refer to derby.log or uncomment this:
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//e.printStackTrace(System.err);
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e = e.getNextException();
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}
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}
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/**
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* Parses the arguments given and sets the values of this class' instance
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* variables accordingly - that is which framework to use, the name of the
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* JDBC driver class, and which connection protocol protocol to use. The
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* protocol should be used as part of the JDBC URL when connecting to Derby.
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* <p>
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* If the argument is "embedded" or invalid, this method will not change
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* anything, meaning that the default values will be used.</p>
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* <p>
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* @param args JDBC connection framework, either "embedded", "derbyclient".
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* Only the first argument will be considered, the rest will be ignored.
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*/
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private void parseArguments(String[] args)
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{
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if (args.length > 0) {
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if (args[0].equalsIgnoreCase("derbyclient"))
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{
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framework = "derbyclient";
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driver = "org.apache.derby.jdbc.ClientDriver";
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protocol = "jdbc:derby://localhost:1527/";
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}
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}
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}
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}
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