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      Java 使用 SQLite

      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。

      • 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。

      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
      
      
      目录
      目录