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  SQLite - Java

  • 简述

    在本章中，您将学习如何在 Java 程序中使用 SQLite。

  • 安装

    在我们的 Java 程序中开始使用 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 教程以在您的机器上安装 Java。现在，让我们检查如何设置 SQLite JDBC 驱动程序。
    • 从sqlite-jdbc存储库下载最新版本的sqlite-jdbc-(VERSION).jar。
    • 将下载的 jar 文件sqlite-jdbc-(VERSION).jar 添加到您的CLASSPATH中，或者您可以将它与 -classpath 选项一起使用，如以下示例中所述。
    以下部分假设您对 Java JDBC 概念知之甚少。如果您不知道，那么建议您花半个小时学习JDBC 教程，以熟悉下面解释的概念。

  • 连接到数据库

    以下 Java 程序显示了如何连接到现有数据库。如果数据库不存在，则将创建它并最终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来创建我们的数据库 test.db在当前目录中。您可以根据需要更改路径。我们假设当前版本的 JDBC 驱动程序sqlite-jdbc-3.7.2.jar在当前路径中可用。 
    
$javac SQLiteJDBC.java
$java -classpath ".:sqlite-jdbc-3.7.2.jar" SQLiteJDBC
Open database successfully
    如果您打算使用 Windows 机器，那么您可以编译并运行您的代码，如下所示 - 
    
$javac SQLiteJDBC.java
$java -classpath ".;sqlite-jdbc-3.7.2.jar" SQLiteJDBC
Opened database successfully

  • 创建表

    下面的 Java 程序将用于在之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");
   }
}
    当上面的程序被编译和执行时，它会在你的目录中创建 COMPANY 表 test.db 该文件的最终清单如下 - 
    
-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

  • 插入操作

    下面的 Java 程序显示了如何在上面示例中创建的 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");
   }
}
    当上述程序被编译和执行时，它会在 COMPANY 表中创建给定的记录，并将显示以下两行 - 
    
Opened database successfully
Records created successfully

  • 选择操作

    以下 Java 程序显示了如何从上面示例中创建的 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");
  }
}
    上述程序编译执行后，会产生如下结果。 
    
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

  • 更新操作

    以下 Java 代码显示了如何使用 UPDATE 语句更新任何记录，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");
   }
}
    上述程序编译执行后，会产生如下结果。 
    
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

  • 删除操作

    以下 Java 代码展示了如何使用 DELETE 语句删除任何记录，然后从我们的 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");
   }
}
    上述程序编译执行后，会产生如下结果。 
    
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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