SQLite – Java
SQLite – Java
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。
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将下载的 jar 文件sqlite-jdbc-(VERSION).jar 添加到您的类路径中，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。如果您不这样做，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，在当前目录中创建我们的数据库test.db。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
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
下面的 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
