Sqlite： Java使用、sqlite-devel

这里写目录标题

一、简介
二、使用
三、更多应用

一、简介

非常轻量级，都没有服务器进程（mysql必须要有mysqld.service 3306）
一个.db或.sqlite文件就是一个数据库, 非常方便备份和传输，只要复制文件就可以

sqlite 是本地数据库，不能远程。安全！
SQLite 在任何时刻只允许一个写入操作执行，其他写入操作需要排队
数据库就是一个文件，这个文件可以在任意位置，任意后缀名，建议用.db 或者 .sqlite 作为后缀

二、使用

1. Java项目中

（1）引入驱动

       <dependency>
            <groupId>org.xerial</groupId>
            <artifactId>sqlite-jdbc</artifactId>
            <version>3.8.11.2</version>
        </dependency>

（2）工具类

SqlLiteHelper

package sample.common.sqlLite;

import sample.common.utils.LogUtil;

import java.lang.reflect.Field;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.logging.Logger;

/**
 * @Author admin
 * @Date 2023/4/4 11:20
 */
public class SqlLiteHelper {
    private Connection connection;
    private Statement statement;
    private ResultSet resultSet;
    private String dbFilePath;   // db文件的位置

    Logger logger = LogUtil.installFormatter(Logger.getLogger(SqlLiteHelper.class.getSimpleName()));

    /**
     * 每次创建都将建立一个连接
     * @param dbFilePath
     * @throws ClassNotFoundException
     * @throws SQLException
     */
    public SqlLiteHelper(String dbFilePath) throws ClassNotFoundException, SQLException{
        this.dbFilePath = dbFilePath;
        connection = getConnection(dbFilePath);
    }

    public Connection getConnection(String dbFilePath) throws ClassNotFoundException, SQLException {
        Connection conn = null;
        Class.forName("org.sqlite.JDBC");
        conn = DriverManager.getConnection("jdbc:sqlite:" + dbFilePath);
        return conn;
    }

    private Connection getConnection() throws ClassNotFoundException, SQLException {
        if (null == connection) connection = getConnection(dbFilePath);
        return connection;
    }

    private Statement getStatement() throws SQLException, ClassNotFoundException {
        if (null == statement) statement = getConnection().createStatement();
        return statement;
    }



    /**返回对象**/
    public <T> T executeQuery(String sql, ResultSetExtractor<T> rse) throws SQLException, ClassNotFoundException {
        try {
            resultSet = getStatement().executeQuery(sql);
            T rs = rse.extractData(resultSet);
            return rs;
        } finally {
            destroyed();
        }
    }
    /**返回对象集合**/
    public <T> List<T> executeQuery(String sql, RowMapper<T> rm) throws SQLException, ClassNotFoundException {
        List<T> rsList = new ArrayList<T>();
        try {
            resultSet = getStatement().executeQuery(sql);
            while (resultSet.next()) {
                rsList.add(rm.mapRow(resultSet, resultSet.getRow()));
            }
        } finally {
            destroyed();
        }
        return rsList;
    }

    public <T> List<T> executeQueryList(String sql, Class<T> clazz) throws SQLException, ClassNotFoundException, IllegalAccessException, InstantiationException {
        List<T> rsList = new ArrayList<T>();
        try {
            resultSet = getStatement().executeQuery(sql);
            while (resultSet.next()) {
                T t = clazz.newInstance();
                for (Field field : t.getClass().getDeclaredFields()) {
                    field.setAccessible(true);
                    field.set(t,resultSet.getObject(field.getName()));
                }
                rsList.add(t);
            }
        } finally {
            destroyed();
        }
        return rsList;
    }
    public <T> T executeQuery(String sql, Class<T> clazz) throws SQLException, ClassNotFoundException, IllegalAccessException, InstantiationException {
        try {
            resultSet = getStatement().executeQuery(sql);
            T t = clazz.newInstance();
            for (Field field : t.getClass().getDeclaredFields()) {
                field.setAccessible(true);
                //  ---> 连接断开了
                field.set(t,resultSet.getObject(field.getName()));
            }
            return t;
        } finally {
            destroyed();
        }
    }
    public int count(String sql) throws SQLException, ClassNotFoundException, IllegalAccessException, InstantiationException {
        try {
            resultSet = getStatement().executeQuery(sql);
            if(resultSet.next()){
                return resultSet.getInt(1);
            }
        } finally {
            destroyed();
        }
        return 0;
    }
    /**返回更新成功的条数**/
    public int executeUpdate(String sql) throws SQLException, ClassNotFoundException {
        try {
            int c = getStatement().executeUpdate(sql);
            return c;
        } finally {
            destroyed();
        }
    }
    /**执行多个更新**/
    public void executeUpdate(String...sqls) throws SQLException, ClassNotFoundException {
        try {
            for (String sql : sqls) {
                getStatement().executeUpdate(sql);
            }
        } finally {
            destroyed();
        }
    }
    public void executeUpdate(List<String> sqls) throws SQLException, ClassNotFoundException {
        try {
            for (String sql : sqls) {
                getStatement().executeUpdate(sql);
            }
        } finally {
            destroyed();
        }
    }
    /**数据插入更新**/
    public int executeInsert(String tableName, Map<String,Object> param) throws SQLException, ClassNotFoundException {
        try {
            StringBuffer sql = new StringBuffer();
            sql.append("INSERT INTO ");
            sql.append(tableName);
            sql.append(" ( ");
            for (String key : param.keySet()) {
                sql.append(key);
                sql.append(",");
            }
            sql.delete(sql.length()-1,sql.length());
            sql.append(")  VALUES ( ");
            for (String key : param.keySet()) {
                sql.append("'");
                sql.append(param.get(key));
                sql.append("',");
            }
            sql.delete(sql.length()-1,sql.length());
            sql.append(");");
            int c = getStatement().executeUpdate(sql.toString());
            return c;
        } finally {
            destroyed();
        }

    }

    /**数据库资源关闭和释放**/
    public void destroyed() {
        // 每一次crud都关闭了所有的资源
        try {
            if (null != statement) {
                statement.close();
                statement = null;
            }

            if (null != connection) {
                connection.close();
                connection = null;
            }

            if (null != resultSet) {
                resultSet.close();
                resultSet = null;
            }


        } catch (SQLException e) {
            logger.info("Sqlite数据库关闭时异常"+e.getMessage());
        }
    }


}

结果集实现

package sample.common.sqlLite;

import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * @Author admin
 * @Date 2023/4/4 11:25
 */
public interface RowMapper<T> {
    public abstract T mapRow(ResultSet rs, int index) throws SQLException;
}

package sample.common.sqlLite;

import java.sql.ResultSet;

/**
 * @Author admin
 * @Date 2023/4/4 11:24
 */
public interface ResultSetExtractor<T> {
    public abstract T extractData(ResultSet resulltSet);
}

（3）调用举例

加载库和表

SqliteHelper sqlLiteHelper = new SqlLiteHelper(dbFilePath);  // 库
String createCard = "create table if not exists card(id integer primary key autoincrement,name text,lastReport text)";
sqlLiteHelper.executeUpdate(createCard); // 建表

2. sqlite-devel in linux

sqlite-devel

centos7.6
https://www.sqlite.org/download.html

yum install sqlite-devel

使用

sqlite 连接不需要用户名和密码

[root@localhost trdp]# sqlite3 trdp.db
SQLite version 3.7.17 2013-05-20 00:56:22
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> .database   
# 输出显示了当前连接的数据库文件路径。
seq  name             file                                                      
---  ---------------  ----------------------------------------------------------
0    main             /usr/local/tynoo/trdp/trdp.db

sqlite> .tables
msgs  port
sqlite> .schema port
CREATE TABLE port
(
    port String
);
sqlite> select * from msgs;
sqlite> insert into port (port) values (null);
sqlite> .quit

三、更多应用

1. 数据类型

https://www.sqlite.net.cn/datatype3.html

2. 如何存储日期和时间

在这里插入图片描述

3. 备份

因为sqlite基于文件存储的特殊特性，
它的备份本质上是这个sqlite_database.db这个文件的备份，尤其是在单用户或低并发场景下，SQLite 3 的数据备份可以通过简单的文件复制cp来实现

但是这里就存在几个问题：
（1）文件被锁定，比如说正在写入数据
（2）事务不一致，你复制的时候，某个事务正在进行中