2021-06-05 09:57  阅读(119)
文章分类:SQLite 教程 文章标签:SQLite
©  原文作者:w3cschool 原文地址:https://www.w3cschool.cn/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
    
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