Sqlite 简明教程

SQLite - Java

在本章中，你将学习如何在 Java 程序中使用 SQLite。

Installation

在你开始在 Java 程序中使用 SQLite 之前，你需要确保已在计算机上设置好 SQLite JDBC 驱动程序和 Java。你可以查看 Java 教程以在计算机上安装 Java。现在，让我们检查如何设置 SQLite JDBC 驱动程序。

  1. 从 sqlite-jdbc 存储库下载最新版本的 sqlite-jdbc-(版本号)。jar。

  2. 在类路径中添加下载的 jar 文件 sqlite-jdbc-(版本号)。 jar，或者可以将其与 -classpath 选项一起使用，如下例所示。

以下部分假定你对 Java JDBC 概念了解不多。如果没有，建议花半小时时间 JDBC Tutorial 熟悉下面解释的概念。

Connect to Database

Following Java 程序展示了如何连接到现有的数据库。如果数据库不存在，则它将被创建，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，让我们编译并运行上述程序在当前目录中创建我们的数据库 test.db 。您可以根据您的要求更改路径。我们假设当前版本的 JDBC 驱动程序 sqlite-jdbc-3.7.2.jar 可在当前路径中使用。

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

如果您要使用 Windows 机器，则可以按照以下方式编译并运行您的代码 −

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

Create a Table

Following 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");
   }
}

当上述程序被编译并执行时，它将在您的 test.db 中创建 COMPANY 表，并且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

INSERT Operation

Following Java 程序展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");
   }
}

当上述程序被编译并执行时，它将在 COMPANY 表中创建给定的记录，并且将显示以下两行 −

Opened database successfully
Records created successfully

SELECT Operation

Following Java 程序展示了如何在上面示例中创建的 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");
  }
}

当以上程序编译并且执行时，它会生成以下结果。

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 Operation

Following Java 代码展示了如何使用 UPDATE 语句来更新任何记录，然后获取并显示 COMPANY 表中更新的记录。

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");
   }
}

当以上程序编译并且执行时，它会生成以下结果。

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 Operation

Following Java 代码展示了如何使用 DELETE 语句删除任何记录，然后获取并显示 COMPANY 表中剩余的记录。

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");
   }
}

当以上程序编译并且执行时，它会生成以下结果。

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