SQLite – Java

安装

在 Java 程序中使用 SQLite 之前，我们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。现在，我们来看看如何在机器上安装 SQLite JDBC 驱动程序。

  • 从 sqlite-jdbc 库下载 sqlite-jdbc-(VERSION).jar 的最新版本。
  • 在您的 class 路径中添加下载的 jar 文件 sqlite-jdbc-(VERSION).jar，或者在 -classpath 选项中使用它，这将在后面的实例中进行讲解。

在学习下面部分的知识之前，您必须对 Java JDBC 概念有初步了解。如果您还未了解相关知识，那么建议您可以先花半个小时学习下 JDBC 教程相关知识，这将有助于您学习接下来讲解的知识。

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。

  1.     import java.sql.*;
  3.     public class SQLiteJDBC
  4.     {
  5.       public static void main( String args[] )
  6.       {
  7.         Connection c = null;
  8.         try {
  9.           Class.forName("org.sqlite.JDBC");
  10.           c = DriverManager.getConnection("jdbc:sqlite:test.db");
  11.         } catch ( Exception e ) {
  12.           System.err.println( e.getClass().getName() + ": " + e.getMessage() );
  13.           System.exit(0);
  14.         }
  15.         System.out.println("Opened database successfully");
  16.       }
  17.     }

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。

  1.     $javac SQLiteJDBC.java
  2.     $java -classpath ".:sqlite-jdbc-3.7.2.jar" SQLiteJDBC
  3.     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：

  1.     $javac SQLiteJDBC.java
  2.     $java -classpath ".;sqlite-jdbc-3.7.2.jar" SQLiteJDBC
  3.     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：

  1.     import java.sql.*;
  3.     public class SQLiteJDBC
  4.     {
  5.       public static void main( String args[] )
  6.       {
  7.         Connection c = null;
  8.         Statement stmt = null;
  9.         try {
  10.           Class.forName("org.sqlite.JDBC");
  11.           c = DriverManager.getConnection("jdbc:sqlite:test.db");
  12.           System.out.println("Opened database successfully");
  14.           stmt = c.createStatement();
  15.           String sql = "CREATE TABLE COMPANY " +
  16.                        "(ID INT PRIMARY KEY     NOT NULL," +
  17.                        " NAME           TEXT    NOT NULL, " +
  18.                        " AGE            INT     NOT NULL, " +
  19.                        " ADDRESS        CHAR(50), " +
  20.                        " SALARY         REAL)";
  21.           stmt.executeUpdate(sql);
  22.           stmt.close();
  23.           c.close();
  24.         } catch ( Exception e ) {
  25.           System.err.println( e.getClass().getName() + ": " + e.getMessage() );
  26.           System.exit(0);
  27.         }
  28.         System.out.println("Table created successfully");
  29.       }
  30.     }

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：

  1.     -rw-r--r--. 1 root root 3201128 Jan 22 19:04 sqlite-jdbc-3.7.2.jar
  2.     -rw-r--r--. 1 root root    1506 May  8 05:43 SQLiteJDBC.class
  3.     -rw-r--r--. 1 root root     832 May  8 05:42 SQLiteJDBC.java
  4.     -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：

  1.     import java.sql.*;
  3.     public class SQLiteJDBC
  4.     {
  5.       public static void main( String args[] )
  6.       {
  7.         Connection c = null;
  8.         Statement stmt = null;
  9.         try {
  10.           Class.forName("org.sqlite.JDBC");
  11.           c = DriverManager.getConnection("jdbc:sqlite:test.db");
  12.           c.setAutoCommit(false);
  13.           System.out.println("Opened database successfully");
  15.           stmt = c.createStatement();
  16.           String sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " +
  17.                        "VALUES (1, 'Paul', 32, 'California', 20000.00 );";
  18.           stmt.executeUpdate(sql);
  20.           sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " +
  21.                 "VALUES (2, 'Allen', 25, 'Texas', 15000.00 );";
  22.           stmt.executeUpdate(sql);
  24.           sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " +
  25.                 "VALUES (3, 'Teddy', 23, 'Norway', 20000.00 );";
  26.           stmt.executeUpdate(sql);
  28.           sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " +
  29.                 "VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 );";
  30.           stmt.executeUpdate(sql);
  32.           stmt.close();
  33.           c.commit();
  34.           c.close();
  35.         } catch ( Exception e ) {
  36.           System.err.println( e.getClass().getName() + ": " + e.getMessage() );
  37.           System.exit(0);
  38.         }
  39.         System.out.println("Records created successfully");
  40.       }
  41.     }

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：

  1.     Opened database successfully
  2.     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：

  1.     import java.sql.*;
  3.     public class SQLiteJDBC
  4.     {
  5.       public static void main( String args[] )
  6.       {
  7.         Connection c = null;
  8.         Statement stmt = null;
  9.         try {
  10.           Class.forName("org.sqlite.JDBC");
  11.           c = DriverManager.getConnection("jdbc:sqlite:test.db");
  12.           c.setAutoCommit(false);
  13.           System.out.println("Opened database successfully");
  15.           stmt = c.createStatement();
  16.           ResultSet rs = stmt.executeQuery( "SELECT * FROM COMPANY;" );
  17.           while ( rs.next() ) {
  18.              int id = rs.getInt("id");
  19.              String  name = rs.getString("name");
  20.              int age  = rs.getInt("age");
  21.              String  address = rs.getString("address");
  22.              float salary = rs.getFloat("salary");
  23.              System.out.println( "ID = " + id );
  24.              System.out.println( "NAME = " + name );
  25.              System.out.println( "AGE = " + age );
  26.              System.out.println( "ADDRESS = " + address );
  27.              System.out.println( "SALARY = " + salary );
  28.              System.out.println();
  29.           }
  30.           rs.close();
  31.           stmt.close();
  32.           c.close();
  33.         } catch ( Exception e ) {
  34.           System.err.println( e.getClass().getName() + ": " + e.getMessage() );
  35.           System.exit(0);
  36.         }
  37.         System.out.println("Operation done successfully");
  38.       }
  39.     }

上述程序编译和执行时，它会产生以下结果：

  1.     Opened database successfully
  2.     ID = 1
  3.     NAME = Paul
  4.     AGE = 32
  5.     ADDRESS = California
  6.     SALARY = 20000.0
  8.     ID = 2
  9.     NAME = Allen
  10.     AGE = 25
  11.     ADDRESS = Texas
  12.     SALARY = 15000.0
  14.     ID = 3
  15.     NAME = Teddy
  16.     AGE = 23
  17.     ADDRESS = Norway
  18.     SALARY = 20000.0
  20.     ID = 4
  21.     NAME = Mark
  22.     AGE = 25
  23.     ADDRESS = Rich-Mond
  24.     SALARY = 65000.0
  26.     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：

  1.     import java.sql.*;
  3.     public class SQLiteJDBC
  4.     {
  5.       public static void main( String args[] )
  6.       {
  7.         Connection c = null;
  8.         Statement stmt = null;
  9.         try {
  10.           Class.forName("org.sqlite.JDBC");
  11.           c = DriverManager.getConnection("jdbc:sqlite:test.db");
  12.           c.setAutoCommit(false);
  13.           System.out.println("Opened database successfully");
  15.           stmt = c.createStatement();
  16.           String sql = "UPDATE COMPANY set SALARY = 25000.00 where ID=1;";
  17.           stmt.executeUpdate(sql);
  18.           c.commit();
  20.           ResultSet rs = stmt.executeQuery( "SELECT * FROM COMPANY;" );
  21.           while ( rs.next() ) {
  22.              int id = rs.getInt("id");
  23.              String  name = rs.getString("name");
  24.              int age  = rs.getInt("age");
  25.              String  address = rs.getString("address");
  26.              float salary = rs.getFloat("salary");
  27.              System.out.println( "ID = " + id );
  28.              System.out.println( "NAME = " + name );
  29.              System.out.println( "AGE = " + age );
  30.              System.out.println( "ADDRESS = " + address );
  31.              System.out.println( "SALARY = " + salary );
  32.              System.out.println();
  33.           }
  34.           rs.close();
  35.           stmt.close();
  36.           c.close();
  37.         } catch ( Exception e ) {
  38.           System.err.println( e.getClass().getName() + ": " + e.getMessage() );
  39.           System.exit(0);
  40.         }
  41.         System.out.println("Operation done successfully");
  42.       }
  43.     }

上述程序编译和执行时，它会产生以下结果：

  1.     Opened database successfully
  2.     ID = 1
  3.     NAME = Paul
  4.     AGE = 32
  5.     ADDRESS = California
  6.     SALARY = 25000.0
  8.     ID = 2
  9.     NAME = Allen
  10.     AGE = 25
  11.     ADDRESS = Texas
  12.     SALARY = 15000.0
  14.     ID = 3
  15.     NAME = Teddy
  16.     AGE = 23
  17.     ADDRESS = Norway
  18.     SALARY = 20000.0
  20.     ID = 4
  21.     NAME = Mark
  22.     AGE = 25
  23.     ADDRESS = Rich-Mond
  24.     SALARY = 65000.0
  26.     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：

  1.     import java.sql.*;
  3.     public class SQLiteJDBC
  4.     {
  5.       public static void main( String args[] )
  6.       {
  7.         Connection c = null;
  8.         Statement stmt = null;
  9.         try {
  10.           Class.forName("org.sqlite.JDBC");
  11.           c = DriverManager.getConnection("jdbc:sqlite:test.db");
  12.           c.setAutoCommit(false);
  13.           System.out.println("Opened database successfully");
  15.           stmt = c.createStatement();
  16.           String sql = "DELETE from COMPANY where ID=2;";
  17.           stmt.executeUpdate(sql);
  18.           c.commit();
  20.           ResultSet rs = stmt.executeQuery( "SELECT * FROM COMPANY;" );
  21.           while ( rs.next() ) {
  22.              int id = rs.getInt("id");
  23.              String  name = rs.getString("name");
  24.              int age  = rs.getInt("age");
  25.              String  address = rs.getString("address");
  26.              float salary = rs.getFloat("salary");
  27.              System.out.println( "ID = " + id );
  28.              System.out.println( "NAME = " + name );
  29.              System.out.println( "AGE = " + age );
  30.              System.out.println( "ADDRESS = " + address );
  31.              System.out.println( "SALARY = " + salary );
  32.              System.out.println();
  33.           }
  34.           rs.close();
  35.           stmt.close();
  36.           c.close();
  37.         } catch ( Exception e ) {
  38.           System.err.println( e.getClass().getName() + ": " + e.getMessage() );
  39.           System.exit(0);
  40.         }
  41.         System.out.println("Operation done successfully");
  42.       }
  43.     }

上述程序编译和执行时，它会产生以下结果：

  1.     Opened database successfully
  2.     ID = 1
  3.     NAME = Paul
  4.     AGE = 32
  5.     ADDRESS = California
  6.     SALARY = 25000.0
  8.     ID = 3
  9.     NAME = Teddy
  10.     AGE = 23
  11.     ADDRESS = Norway
  12.     SALARY = 20000.0
  14.     ID = 4
  15.     NAME = Mark
  16.     AGE = 25
  17.     ADDRESS = Rich-Mond
  18.     SALARY = 65000.0
  20.     Operation done successfully