Java 操作SQLite的例子
Java 操作SQLite的例子
在本章中,您将学习如何在Java程序中使用SQLite。
安装
在开始在我们的Java程序中使用SQLite之前,您需要确保在机器上设置了SQLite JDBC驱动程序和Java。您可以查看Java教程,了解计算机上的Java安装。现在,让我们来看看如何设置SQLite JDBC驱动程序。
下载最新版本的sqlite-jdbc.jar驱动。
添加jar包到你java项目的classpath中,这个取决于你环境变量的classpath设置和ide工具的配置。
以下部分假设您已经对Java JDBC概念有了一点了解。如果没有,那么建议花半个小时学习JDBC教程,以适应下面解释的概念。
连接数据库
以下Java程序展示了如何连接到现有数据库。如果数据库不存在,那么它将被创建,最后返回一个数据库对象。
import java.sql.*; public class SQLiteJDBC { public static void main( String args[] ) { Connection c = null; try { Class.forName("org.sqlite.JDBC"); c = DriverManager.getConnection("jdbc:sqlite:test.db"); } catch ( Exception e ) { System.err.println( e.getClass().getName() + ": " + e.getMessage() ); System.exit(0); } System.out.println("Opened database successfully"); } }
现在,让我们编译并运行上面的程序,它将在当前目录中创建数据库test.db。你可以根据要求改变你的路径。
$javac SQLiteJDBC.java $java -classpath ".:sqlite-jdbc-3.7.2.jar" SQLiteJDBC Open database successfully
创建表
下面的Java程序将在上面例子中创建的数据库中新建一张表。
import java.sql.*; public class SQLiteJDBC { public static void main( String args[] ) { Connection c = null; Statement stmt = null; try { Class.forName("org.sqlite.JDBC"); c = DriverManager.getConnection("jdbc:sqlite:test.db"); System.out.println("Opened database successfully"); stmt = c.createStatement(); String sql = "CREATE TABLE COMPANY " + "(ID INT PRIMARY KEY NOT NULL," + " NAME TEXT NOT NULL, " + " AGE INT NOT NULL, " + " ADDRESS CHAR(50), " + " SALARY REAL)"; stmt.executeUpdate(sql); stmt.close(); c.close(); } catch ( Exception e ) { System.err.println( e.getClass().getName() + ": " + e.getMessage() ); System.exit(0); } System.out.println("Table created successfully"); } }
当编译并执行上述程序时,它将在你的test.db中创建COMPANY表,文件的最终列表如下所示:
-rw-r--r--. 1 root root 3201128 Jan 22 19:04 sqlite-jdbc-3.7.2.jar -rw-r--r--. 1 root root 1506 May 8 05:43 SQLiteJDBC.class -rw-r--r--. 1 root root 832 May 8 05:42 SQLiteJDBC.java -rw-r--r--. 1 root root 3072 May 8 05:43 test.db
INSERT操作
下面的Java程序展示了如何在COMPANY表中增加记录。
import java.sql.*; public class SQLiteJDBC { public static void main( String args[] ) { Connection c = null; Statement stmt = null; try { Class.forName("org.sqlite.JDBC"); c = DriverManager.getConnection("jdbc:sqlite:test.db"); c.setAutoCommit(false); System.out.println("Opened database successfully"); stmt = c.createStatement(); String sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " + "VALUES (1, 'Paul', 32, 'California', 20000.00 );"; stmt.executeUpdate(sql); sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " + "VALUES (2, 'Allen', 25, 'Texas', 15000.00 );"; stmt.executeUpdate(sql); sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " + "VALUES (3, 'Teddy', 23, 'Norway', 20000.00 );"; stmt.executeUpdate(sql); sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " + "VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 );"; stmt.executeUpdate(sql); stmt.close(); c.commit(); c.close(); } catch ( Exception e ) { System.err.println( e.getClass().getName() + ": " + e.getMessage() ); System.exit(0); } System.out.println("Records created successfully"); } }
当上述程序被编译和执行时,它将在COMPANY表中增加指定的记录,并将显示以下两行:
Opened database successfully Records created successfully
SELECT操作
下面的Java程序展示了如何从COMPANY表中获取和显示记录。
import java.sql.*; public class SQLiteJDBC { public static void main( String args[] ) { Connection c = null; Statement stmt = null; try { Class.forName("org.sqlite.JDBC"); c = DriverManager.getConnection("jdbc:sqlite:test.db"); c.setAutoCommit(false); System.out.println("Opened database successfully"); stmt = c.createStatement(); ResultSet rs = stmt.executeQuery( "SELECT * FROM COMPANY;" ); while ( rs.next() ) { int id = rs.getInt("id"); String name = rs.getString("name"); int age = rs.getInt("age"); String address = rs.getString("address"); float salary = rs.getFloat("salary"); System.out.println( "ID = " + id ); System.out.println( "NAME = " + name ); System.out.println( "AGE = " + age ); System.out.println( "ADDRESS = " + address ); System.out.println( "SALARY = " + salary ); System.out.println(); } rs.close(); stmt.close(); c.close(); } catch ( Exception e ) { System.err.println( e.getClass().getName() + ": " + e.getMessage() ); System.exit(0); } System.out.println("Operation done successfully"); } }
当编译并执行上述程序时,它将产生以下结果。
Opened database successfully ID = 1 NAME = Paul AGE = 32 ADDRESS = California SALARY = 20000.0 ID = 2 NAME = Allen AGE = 25 ADDRESS = Texas SALARY = 15000.0 ID = 3 NAME = Teddy AGE = 23 ADDRESS = Norway SALARY = 20000.0 ID = 4 NAME = Mark AGE = 25 ADDRESS = Rich-Mond SALARY = 65000.0 Operation done successfully
UPDATE操作
下面的Java代码展示了如何使用UPDATE语句更新记录,然后从COMPANY表中获取并显示更新的记录。
import java.sql.*; public class SQLiteJDBC { public static void main( String args[] ) { Connection c = null; Statement stmt = null; try { Class.forName("org.sqlite.JDBC"); c = DriverManager.getConnection("jdbc:sqlite:test.db"); c.setAutoCommit(false); System.out.println("Opened database successfully"); stmt = c.createStatement(); String sql = "UPDATE COMPANY set SALARY = 25000.00 where ID=1;"; stmt.executeUpdate(sql); c.commit(); ResultSet rs = stmt.executeQuery( "SELECT * FROM COMPANY;" ); while ( rs.next() ) { int id = rs.getInt("id"); String name = rs.getString("name"); int age = rs.getInt("age"); String address = rs.getString("address"); float salary = rs.getFloat("salary"); System.out.println( "ID = " + id ); System.out.println( "NAME = " + name ); System.out.println( "AGE = " + age ); System.out.println( "ADDRESS = " + address ); System.out.println( "SALARY = " + salary ); System.out.println(); } rs.close(); stmt.close(); c.close(); } catch ( Exception e ) { System.err.println( e.getClass().getName() + ": " + e.getMessage() ); System.exit(0); } System.out.println("Operation done successfully"); } }
当编译并执行上述程序时,它将产生以下结果。
Opened database successfully ID = 1 NAME = Paul AGE = 32 ADDRESS = California SALARY = 25000.0 ID = 2 NAME = Allen AGE = 25 ADDRESS = Texas SALARY = 15000.0 ID = 3 NAME = Teddy AGE = 23 ADDRESS = Norway SALARY = 20000.0 ID = 4 NAME = Mark AGE = 25 ADDRESS = Rich-Mond SALARY = 65000.0 Operation done successfully
DELETE 操作
下面的Java代码展示了如何使用DELETE语句删除记录,然后从COMPANY表中获取并显示剩余的记录。
import java.sql.*; public class SQLiteJDBC { public static void main( String args[] ) { Connection c = null; Statement stmt = null; try { Class.forName("org.sqlite.JDBC"); c = DriverManager.getConnection("jdbc:sqlite:test.db"); c.setAutoCommit(false); System.out.println("Opened database successfully"); stmt = c.createStatement(); String sql = "DELETE from COMPANY where ID=2;"; stmt.executeUpdate(sql); c.commit(); ResultSet rs = stmt.executeQuery( "SELECT * FROM COMPANY;" ); while ( rs.next() ) { int id = rs.getInt("id"); String name = rs.getString("name"); int age = rs.getInt("age"); String address = rs.getString("address"); float salary = rs.getFloat("salary"); System.out.println( "ID = " + id ); System.out.println( "NAME = " + name ); System.out.println( "AGE = " + age ); System.out.println( "ADDRESS = " + address ); System.out.println( "SALARY = " + salary ); System.out.println(); } rs.close(); stmt.close(); c.close(); } catch ( Exception e ) { System.err.println( e.getClass().getName() + ": " + e.getMessage() ); System.exit(0); } System.out.println("Operation done successfully"); } }
当编译并执行上述程序时,它将产生以下结果。
Opened database successfully ID = 1 NAME = Paul AGE = 32 ADDRESS = California SALARY = 25000.0 ID = 3 NAME = Teddy AGE = 23 ADDRESS = Norway SALARY = 20000.0 ID = 4 NAME = Mark AGE = 25 ADDRESS = Rich-Mond SALARY = 65000.0 Operation done successfully