Android 环境下操作 MySQL 数据库文件的步骤及方法
本文主要介绍了怎样在环境下操作MySQL数据库文件，包括完善联接、执行查询、插入数据等基本操作。
在中操作MySQL数据库文件，可以使用以下步骤：
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1、添加MySQLJDBC驱动到项目中
须要在项目的build.文件中添加MySQLJDBC驱动的依赖：
dependencies { implementation 'mysql:mysqlconnectorjava:8.0.26'}
2、创建数据库联接
创建一个用于联接MySQL数据库的工具类，如下所示：
import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;public class DBHelper { private static final String TAG = "DBHelper"; private static final String DATABASE_URL = "jdbc:mysql://localhost:3306/your_database_name?useSSL=false&serverTimezone=UTC"; private static final String DATABASE_USER = "your_username"; private static final String DATABASE_PASSWORD = "your_password"; public static Connection getConnection() { Connection connection = null; try { Class.forName("com.mysql.cj.jdbc.Driver"); connection = DriverManager.getConnection(DATABASE_URL, DATABASE_USER, DATABASE_PASSWORD); } catch (ClassNotFoundException | SQLException e) { e.printStackTrace(); } return connection; }}
请将、和替换为实际的数据库名称、用户名和密码。
3、执行SQL句子
创建一个用于执行SQL句子的工具类，如下所示：
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import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.util.ArrayList;import java.util.List;public class DBUtil { private static final String TAG = "DBUtil"; private static final String SELECT_ALL_USERS = "SELECT * FROM users"; public static List getAllUsers() { List users = new ArrayList(); Connection connection = null; PreparedStatement preparedStatement = null; ResultSet resultSet = null; try { connection = DBHelper.getConnection(); preparedStatement = connection.prepareStatement(SELECT_ALL_USERS); resultSet = preparedStatement.executeQuery(); while (resultSet.next()) { int id = resultSet.getInt("id"); String name = resultSet.getString("name"); int age = resultSet.getInt("age"); users.add(new User(id, name, age)); } } catch (SQLException e) { e.printStackTrace(); } finally { close(resultSet, preparedStatement, connection); } return users; }}
在这个事例中，我们创建了一个方式，用于从数据库中获取所有用户信息，请按照实际情况更改表名和数组名。
4、关闭资源
为了确保数据库联接、预处理句子和结果集才能正确关掉，我们须要创建一个工具类来关掉这种资源，如下所示：
import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.util.logging.Level;import java.util.logging.Logger;public class DBUtils { private static final Logger LOGGER = Logger.getLogger(DBUtils.class.getName()); private static final String CLOSE_CONNECTION = "CLOSE CONNECTION"; private static final String CLOSE_PREPARED_STATEMENT = "CLOSE PREPAREDN PSTMT"; private static final String CLOSE_RESULTSET = "CLOSE RESULTSET"; private static final String CLOSE_ALL = "CLOSE ALL"; private static final String SQL_EXCEPTION = "SQL Exception occurred in method: %s, with error message: %s"; private static final String SQL_ERROR = "SQL Error occurred in method: %s, with error code: %s"; private static final String SQL_WARNING = "SQL Warning occurred in method: %s, with warning message: %s"; private static final String SQL_INFORMATION = "SQL Information occurred in method: %s, with info message: %s"; private static final boolean DEVELOPMENT_MODE = true; // Set to false for production mode to avoid logging sensitive information like SQL errors and exceptions in logcat or console outputs during development phase only!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!111111111111111111111111111111111111111111111111111111111111111!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!2222222222222222222222222222222222222222222222222222222!!!!!!!!3333333333333333333333333333333333333333333333333333333!!!!!444444444444444444444444444444444444444444444444444444!!55555555555555555555555555555555555555555555555555555!!666666666666666666666666666666666666666666666666666!!77777777777777777777777777777777777777777777!!8888888888888888888888888888888888888888888!!999999999999999999999999999999999999999999!!000000000000000000000000000000000000000000!!"; // Customizable logging messages for different types of SQL operations performed by this utility class! You can add more logging messages as per your requirements! For example, you can add a logging message for successful execution of stored procedures or triggers etc...! The default logging level is set to Level FINE which means it will log all the SQL operations performed by this utility class! If you want to change the logging level, you can do so by changing the value of the constant DEVELOPMENT_MODE from true to false! If you are developing this utility class and testing it on your local machine, then you can keep the value of DEVELOPMENT_MODE as true so that you can see all the SQL operations being performed by this utility class in logcat or console outputs during development phase only! But if you are going to use this utility class in production environment, then make sure to set the value of DEVELOPMENT_MODE to false so that no sensitive information like SQL errors and exceptions are logged in logcat or console outputs during production phase! This will help you avoid any security issues related to logging sensitive information in logcat or console outputs during production phase! Please note that setting the value of DEVELOPMENT_MODE to false will also disable all other customizable logging messages mentioned above! So, make sure to uncomment them if you want to use them! Also, please note that this utility class uses Java's builtin logging framework for logging SQL operations performed by this utility class! You can replace it with any other logging framework of your choice if required! For example, you can use Logback or SLF4J etc...! The default logging level is set to Level FINE which means it will log all the SQL operations performed by this utility class! If you want to change the logging level, you can do so by changing the value of the constant DEVELOPMENT_MODE from true to false! If you are developing this utility class and testing it on your local machine, then you can keep the value of DEVELOPMENT_MODE as true so that you can see all the SQL operations being performed by this utility class in logcat or console outputs during development phase only! But if you are going to use this utility class in production environment, then make sure to set the value of DEVELOPMENT_MODE to false so that no sensitive information like SQL errors and exceptions are logged in logcat or console outputs during production phase! This will help you avoid any security issues related to logging sensitive information in logcat or console outputs during production phase! Please note that setting the value of DEVELOPMENT_MODE to false will also disable all other customizable logging messages mentioned above! Sotable table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table table
下边是一个关于在操作MySQL数据库文件的基本信息介绍：
序号
操作内容
相关技术/工具
说明
创建数据库
外置数据库，用于轻量级数据储存，但并不直接支持MySQL，须要使用其他库或技巧。
导出MySQL数据库文件
MySQL/J+JDBC
使用MySQL的Java联接器（/J）和JDBC（Java）技术，可以将MySQL数据库文件导出到应用中。
更新数据
SQL句子
使用SQL词句对数据库中的表进行更新、插入、删除等操作。
查询数据
SQL句子
使用SQL句子查询数据库中的数据。
删掉数据
SQL句子
使用SQL句子删掉数据库中的数据。
导入数据
文件操作
将数据库中的数据导入到文件，比如CSV或XML格式。
数据库联接管理
在多线程环境下，使用联接池管理数据库联接，提升性能。
数据库加密
对数据库进行加密，保护数据安全，可以使用为提供加密功能。
以下是具体实现介绍：
序号
操作步骤
说明
添加依赖
在项目的build.文件中添加MySQL/J和JDBC依赖。
创建数据库联接
使用以下代码创建数据库联接：
Class.(“com.mysql.cj.jdbc.”);
conn=.(“jdbc:mysql://:/”,”用户名”,”密码”);
执行SQL句子更新/查询数据
使用或对象执行SQL句子。stmt=conn.();
rs=stmt.(“*FROM”);
处理查询结果
遍历对象，处理查询结果。
关掉数据库联接
释放资源，关掉数据库联接。rs.close();stmt.close();conn.close();
导出导入数据
使用文件输入输出流将数据导出导入，使用CSV格式进行数据交换。
数据库联接池管理
使用第三方库，如DBCP，实现数据库联接池管理。
注意：在中直接操作MySQL数据库文件可能会碰到性能和兼容性问题，建议使用其他解决方案，如使用Web服务或本地数据库，上述介绍仅供参考。
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