SqlSessionFactoryBuilder与openSession重载

package com.fly.test;

import com.fly.entity.Student;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.Properties;

public class BuildMethodDemo {

    public static void main(String[] args) throws IOException {
        String resource = "mybatis-config.xml";

        // ========== 方式 1：build(InputStream) —— 使用默认环境 ==========
        System.out.println("========== build 方式 1：使用默认环境（development）==========");
        try (InputStream is = Resources.getResourceAsStream(resource)) {
            SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);
            try (SqlSession session = factory.openSession()) {
                List<Student> list = session.selectList("com.fly.mapper.StudentMapper.findAll");
                System.out.println("默认环境查询到 " + list.size() + " 条记录");
            }
        }

        // ========== 方式 2：build(InputStream, environment) —— 切换到生产环境 ==========
        System.out.println("\n========== build 方式 2：显式指定 production 环境 ==========");
        try (InputStream is = Resources.getResourceAsStream(resource)) {
            SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is, "production");
            System.out.println("【环境切换】已切换到 production 环境，连接至 192.168.1.100");
            // 实际执行查询...
        }

        // ========== 方式 3：build(InputStream, Properties) —— 外部属性覆盖密码 ==========
        System.out.println("\n========== build 方式 3：外部 Properties 覆盖数据库密码 ==========");
        try (InputStream is = Resources.getResourceAsStream(resource)) {
            // 从环境变量或配置中心读取真实密码，覆盖 XML 中的占位符
            Properties externalProps = new Properties();
            externalProps.setProperty("jdbc.dev.password", System.getenv("DB_DEV_PASSWORD"));
            // 若环境变量未设置，使用默认值演示
            if (externalProps.getProperty("jdbc.dev.password") == null) {
                externalProps.setProperty("jdbc.dev.password", "override_dev_123");
            }

            SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is, externalProps);
            System.out.println("【属性覆盖】外部 Properties 已覆盖 jdbc.dev.password");
            System.out.println("【安全提示】生产环境密码不应硬编码在 XML 或 properties 文件中");
        }

        // ========== 方式 4：build(InputStream, environment, Properties) —— 复合场景 ==========
        System.out.println("\n========== build 方式 4：指定环境 + 外部属性覆盖 ==========");
        try (InputStream is = Resources.getResourceAsStream(resource)) {
            Properties externalProps = new Properties();
            externalProps.setProperty("jdbc.prod.password", "override_prod_456");

            SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is, "production", externalProps);
            System.out.println("【复合配置】环境=production，且密码被外部属性覆盖");
        }

        // ========== 方式 5：build(Configuration) —— 纯代码配置 ==========
        System.out.println("\n========== build 方式 5：纯代码构建 Configuration ==========");
        org.apache.ibatis.session.Configuration config = new org.apache.ibatis.session.Configuration();
        config.setEnvironment(new org.apache.ibatis.mapping.Environment(
            "code_env",
            new org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory(),
            new org.apache.ibatis.datasource.pooled.PooledDataSource(
                "com.mysql.cj.jdbc.Driver",
                "jdbc:mysql://localhost:3306/school_dev?useSSL=false&serverTimezone=Asia/Shanghai",
                "root",
                "123456"
            )
        ));
        config.addMapper(com.fly.mapper.StudentMapper.class);

        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(config);
        try (SqlSession session = factory.openSession()) {
            List<Student> list = session.selectList("com.fly.mapper.StudentMapper.findAll");
            System.out.println("纯代码配置查询到 " + list.size() + " 条记录");
        }
    }
}

package com.fly.test;

import com.fly.entity.Student;
import com.fly.util.MyBatisUtil;
import org.apache.ibatis.session.ExecutorType;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.TransactionIsolationLevel;

import java.math.BigDecimal;
import java.sql.Connection;
import java.util.List;

public class OpenSessionDemo {

    public static void main(String[] args) {
        SqlSessionFactory factory = MyBatisUtil.getSqlSessionFactory();

        // ========== 方式 1：openSession() —— 默认手动提交，SIMPLE 执行器 ==========
        System.out.println("========== openSession 方式 1：默认配置（推荐）==========");
        try (SqlSession session = factory.openSession()) {
            System.out.println("【配置】autoCommit=" + session.getConnection().getAutoCommit()
                + ", 执行器=SIMPLE");
            Student student = session.selectOne("com.fly.mapper.StudentMapper.findById", 1);
            System.out.println("查询结果: " + student.getName());
            // DML 需要手动 commit
        } catch (Exception e) {
            e.printStackTrace();
        }

        // ========== 方式 2：openSession(true) —— 自动提交 ==========
        System.out.println("\n========== openSession 方式 2：自动提交模式 ==========");
        try (SqlSession session = factory.openSession(true)) {
            System.out.println("【配置】autoCommit=true，每条 DML 自动提交");
            Student newbie = new Student("自动提交学生", 20, "测试专业", new BigDecimal("80.00"));
            int rows = session.insert("com.fly.mapper.StudentMapper.insertStudent", newbie);
            System.out.println("【插入】影响行数: " + rows + "（已自动提交，无需手动 commit）");
            // 注意：此模式下无法 rollback
        } catch (Exception e) {
            e.printStackTrace();
        }

        // ========== 方式 3：openSession(TransactionIsolationLevel) —— 显式隔离级别 ==========
        System.out.println("\n========== openSession 方式 3：指定 READ_COMMITTED ==========");
        try (SqlSession session = factory.openSession(TransactionIsolationLevel.READ_COMMITTED)) {
            Connection conn = session.getConnection();
            System.out.println("【配置】隔离级别=" + conn.getTransactionIsolation()
                + "（Connection.TRANSACTION_READ_COMMITTED=" + Connection.TRANSACTION_READ_COMMITTED + ")");
            List<Student> list = session.selectList("com.fly.mapper.StudentMapper.findAll");
            System.out.println("查询到 " + list.size() + " 条记录");
        } catch (Exception e) {
            e.printStackTrace();
        }

        // ========== 方式 4：openSession(ExecutorType.BATCH) —— 批量执行器 ==========
        System.out.println("\n========== openSession 方式 4：BATCH 执行器（批量插入）==========");
        try (SqlSession session = factory.openSession(ExecutorType.BATCH)) {
            System.out.println("【配置】ExecutorType=BATCH，多条 INSERT 合并发送");
            String statement = "com.fly.mapper.StudentMapper.insertStudent";

            // 模拟批量插入 3 条记录
            session.insert(statement, new Student("批量学生A", 20, "批量专业", new BigDecimal("70.00")));
            session.insert(statement, new Student("批量学生B", 21, "批量专业", new BigDecimal("75.00")));
            session.insert(statement, new Student("批量学生C", 22, "批量专业", new BigDecimal("80.00")));

            // BATCH 模式下，insert 返回的是批量队列中的序号，而非真实影响行数
            // 必须 flushStatements 后才能获取真实结果
            List<org.apache.ibatis.executor.BatchResult> batchResults = session.flushStatements();
            int totalRows = batchResults.stream().mapToInt(r -> r.getUpdateCounts().length).sum();
            System.out.println("【批量执行】待提交语句数: " + batchResults.size() + ", 影响记录数: " + totalRows);

            session.commit();
            System.out.println("【提交】批量插入已提交");
        } catch (Exception e) {
            e.printStackTrace();
        }

        // ========== 方式 5：openSession(ExecutorType, boolean) —— 执行器 + 自动提交 ==========
        System.out.println("\n========== openSession 方式 5：REUSE + 手动提交 ==========");
        try (SqlSession session = factory.openSession(ExecutorType.REUSE, false)) {
            System.out.println("【配置】ExecutorType=REUSE，复用 PreparedStatement");
            String statement = "com.fly.mapper.StudentMapper.findById";
            // 同一会话内多次执行相同 SQL，PreparedStatement 会被复用
            Student s1 = session.selectOne(statement, 1);
            Student s2 = session.selectOne(statement, 2);
            Student s3 = session.selectOne(statement, 3);
            System.out.println("复用查询结果: " + s1.getName() + ", " + s2.getName() + ", " + s3.getName());
        } catch (Exception e) {
            e.printStackTrace();
        }

        // ========== 最终验证数据状态 ==========
        System.out.println("\n========== 最终数据状态 ==========");
        try (SqlSession session = factory.openSession()) {
            List<Student> list = session.selectList("com.fly.mapper.StudentMapper.findAll");
            System.out.println("当前共 " + list.size() + " 条记录:");
            list.forEach(s -> System.out.println("  " + s));
        }
    }
}