运维入门——SQLite接口——Java

SQLite——Java

安装

在Java程序中使用SQLite之前，需要确保机器上已经有SQLite JDBC Driver驱动程序和Java。可以查看Java教程了解如何在计算机上安装Java。

连接数据库

下面的JAVA程序显示了如何连接到一个现有的数据库。如果数据库不存在，那么它就会被创建，最后将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，让我们来编译和运行上面的程序，在当前目录中创建我们的数据库 test.db。您可以根据需要改变路径。我们假设当前路径下可用的 JDBC 驱动程序的版本是 sqlite-jdbc-3.7.2.jar。

$javac SQLiteJDBC.java

$java -classpath ".:sqlite-jdbc-3.7.2.jar" SQLiteJDBC

Open database successfully

如果您想要使用 Windows 机器，可以按照下列所示编译和运行您的代码：

$javac SQLiteJDBC.java

$java -classpath ".;sqlite-jdbc-3.7.2.jar" SQLiteJDBC

Opened database successfully


创建表

下面的 Java 程序将用于在先前创建的数据库中创建一个表：

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");

}

}

上述程序编译和执行时，它会在 test.db 中创建 COMPANY 表，最终文件列表如下所示：

-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 代码显示了如何在上面创建的 COMPANY 表中创建记录：

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");

}

}

上述程序编译和执行时，它会在 COMPANY 表中创建给定记录，并会显示以下两行：

Opened database successfully

Records created successfully


SELECT 操作

下面的 Java 程序显示了如何从前面创建的 COMPANY 表中获取并显示记录：

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");

}

}

上述程序编译和执行时，它会产生以下结果：

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 代码显示了如何使用 UPDATE 语句来更新任何记录，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");

}

}

上述程序编译和执行时，它会产生以下结果：

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 代码显示了如何使用 DELETE 语句删除任何记录，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");

}

}

上述程序编译和执行时，它会产生以下结果：

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



end

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