无涯教程

时间:2024-01-23 21:33:20

在本章中,您将学习如何在Java程序中使用SQLite。

安装

在无涯教程的Java程序中开始使用SQLite之前,需要确保已在计算机上设置了SQLite JDBC驱动程序和Java。您可以检查Java教程以在计算机上安装Java。现在,让无涯教程检查一下如何设置SQLite JDBC驱动程序。

  • 从sqlite-jdbc存储库。

  • 在类路径中添加下载的jar文件 sqlite-jdbc-(VERSION).jar ,也可以将其与-classpathoptions一起使用,如以下示例中所述。

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,则将创建该数据库,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,让无涯教程编译并运行上述程序,以在当前目录中创建数据库 test.db 。您可以根据需要更改路径。无涯教程假设当前路径中提供了JDBC驱动程序 sqlite-jdbc-3.7.2.jar 的当前版本。

$javac SQLiteJDBC.java
$java -classpath ".:sqlite-jdbc-3.7.2.jar" SQLiteJDBC
Open database successfully

如果要使用Windows计算机,则可以按以下方式编译和运行代码-

$javac SQLiteJDBC.java
$java -classpath ".;sqlite-jdbc-3.7.2.jar" SQLiteJDBC
Opened database successfully

创建表

以下Java程序将用于在先前创建的数据库中创建表。

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");
   }
}

编译并执行上述程序后,它将在 test.db 中创建COMPANY表,文件的最终列表如下-

-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

以下Java程序显示了如何在上面的Example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");
   }
}

当上面的程序被编译和执行时,它将在COMPANY表中创建给定的记录,并显示以下两行-

Opened database successfully
Records created successfully

选择操作

以下Java程序演示了如何从上面的Example中创建的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");
  }
}

编译并执行上述程序后,将产生以下输出。

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");
   }
}

编译并执行上述程序后,将产生以下输出。

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表中获取并显示其余记录。

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");
   }
}

编译并执行上述程序后,将产生以下输出。

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

参考链接

https://www.learnfk.com/sqlite/sqlite-java.html