在这个H2 内存数据库示例中，我们将数据库内容存储在系统的内存中。这里持久性发生在系统的内存上。在这个例子中，我们正在创建一个 java 类，展示如何加载驱动程序、创建数据库、创建表并将一些值插入到表中

H2是 Java SQL 数据库的开源软件实现。H2的主要特点是。

• 非常快，开源，JDBC API
• 嵌入式和服务器模式；内存数据库
• 基于浏览器的控制台应用程序
• 占用空间小：大约 1.5 MB jar 文件大小

所需的库

对于使用 H2 数据库，您需要下载

1. h2-1.4.182.jar

项目结构

使用内存的 H2 数据库

在这里，我们展示了使用 H2 内存数据库的 SQL 语句和 PreparedStatement 的实现。

在下面的代码中，您可以看到我们使用以下 H2 JDBC URL jdbc:h2:mem:test;DB_CLOSE_DELAY=-1来连接数据库

通过以下方式，将H2数据库内容存储在系统内存中

package com.h2.examples;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

// H2 In-Memory Database Example shows about storing the database contents into memory.

public class H2MemoryDatabaseExample {

    private static final String DB_DRIVER = "org.h2.Driver";
    private static final String DB_CONNECTION = "jdbc:h2:mem:test;DB_CLOSE_DELAY=-1";
    private static final String DB_USER = "";
    private static final String DB_PASSWORD = "";

    public static void main(String[] args) throws Exception {
        try {
            insertWithStatement();
            insertWithPreparedStatement();

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private static void insertWithPreparedStatement() throws SQLException {
        Connection connection = getDBConnection();
        PreparedStatement createPreparedStatement = null;
        PreparedStatement insertPreparedStatement = null;
        PreparedStatement selectPreparedStatement = null;

        String CreateQuery = "CREATE TABLE PERSON(id int primary key, name varchar(255))";
        String InsertQuery = "INSERT INTO PERSON" + "(id, name) values" + "(?,?)";
        String SelectQuery = "select * from PERSON";

        try {
            connection.setAutoCommit(false);

            createPreparedStatement = connection.prepareStatement(CreateQuery);
            createPreparedStatement.executeUpdate();
            createPreparedStatement.close();

            insertPreparedStatement = connection.prepareStatement(InsertQuery);
            insertPreparedStatement.setInt(1, 1);
            insertPreparedStatement.setString(2, "Jose");
            insertPreparedStatement.executeUpdate();
            insertPreparedStatement.close();

            selectPreparedStatement = connection.prepareStatement(SelectQuery);
            ResultSet rs = selectPreparedStatement.executeQuery();
            System.out.println("H2 In-Memory Database inserted through PreparedStatement");
            while (rs.next()) {
                System.out.println("Id " + rs.getInt("id") + " Name " + rs.getString("name"));
            }
            selectPreparedStatement.close();

            connection.commit();
        } catch (SQLException e) {
            System.out.println("Exception Message " + e.getLocalizedMessage());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            connection.close();
        }
    }

    private static void insertWithStatement() throws SQLException {
        Connection connection = getDBConnection();
        Statement stmt = null;
        try {
            connection.setAutoCommit(false);
            stmt = connection.createStatement();
            stmt.execute("CREATE TABLE PERSON(id int primary key, name varchar(255))");
            stmt.execute("INSERT INTO PERSON(id, name) VALUES(1, 'Anju')");
            stmt.execute("INSERT INTO PERSON(id, name) VALUES(2, 'Sonia')");
            stmt.execute("INSERT INTO PERSON(id, name) VALUES(3, 'Asha')");

            ResultSet rs = stmt.executeQuery("select * from PERSON");
            System.out.println("H2 In-Memory Database inserted through Statement");
            while (rs.next()) {
                System.out.println("Id " + rs.getInt("id") + " Name " + rs.getString("name"));
            }

            stmt.execute("DROP TABLE PERSON");
            stmt.close();
            connection.commit();
        } catch (SQLException e) {
            System.out.println("Exception Message " + e.getLocalizedMessage());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            connection.close();
        }
    }

    private static Connection getDBConnection() {
        Connection dbConnection = null;
        try {
            Class.forName(DB_DRIVER);
        } catch (ClassNotFoundException e) {
            System.out.println(e.getMessage());
        }
        try {
            dbConnection = DriverManager.getConnection(DB_CONNECTION, DB_USER, DB_PASSWORD);
            return dbConnection;
        } catch (SQLException e) {
            System.out.println(e.getMessage());
        }
        return dbConnection;
    }
}

输出

H2 In-Memory Database inserted through Statement
Id 1 Name Anju
Id 2 Name Sonia
Id 3 Name Asha
H2 In-Memory Database inserted through PreparedStatement
Id 1 Name Jose