fix(h2): honor spring.datasource settings and preserve proxy-aware H2 console redirects

src/main/java/com/example/scaffold/config/database/DatabaseConfig.java

@@ -0,0 +1,79 @@
+package com.example.scaffold.config.database;
+
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.jdbc.DataSourceBuilder;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Profile;
+
+import javax.sql.DataSource;
+
+/**
+ * 多数据库配置 - H2 / MySQL / PostgreSQL
+ * 
+ * 学习要点：
+ * 1. @Profile - 根据环境选择配置
+ * 2. 数据源配置
+ * 3. 连接池配置
+ */
+@Slf4j
+@Configuration
+public class DatabaseConfig {
+    
+    /**
+     * H2 内存数据库 - 开发测试用（默认）
+     */
+    @Bean
+    @Profile("!mysql & !postgresql")
+    @ConditionalOnMissingBean(DataSource.class)
+    public DataSource h2DataSource(
+            @Value("${spring.datasource.url:jdbc:h2:mem:springboot_scaffold_learn;MODE=MYSQL;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE}") String url,
+            @Value("${spring.datasource.username:sa}") String username,
+            @Value("${spring.datasource.password:}") String password) {
+        log.info("🚀 使用 H2 数据库: {}", url);
+        return DataSourceBuilder.create()
+            .driverClassName("org.h2.Driver")
+            .url(url)
+            .username(username)
+            .password(password)
+            .build();
+    }
+    
+    /**
+     * MySQL 数据库
+     */
+    @Bean
+    @Profile("mysql")
+    public DataSource mysqlDataSource(
+            @Value("${DB_URL:jdbc:mysql://localhost:3306/springboot_scaffold}") String url,
+            @Value("${DB_USER:root}") String username,
+            @Value("${DB_PASS:}") String password) {
+        log.info("🚀 使用 MySQL 数据库: {}", url);
+        return DataSourceBuilder.create()
+            .driverClassName("com.mysql.cj.jdbc.Driver")
+            .url(url)
+            .username(username)
+            .password(password)
+            .build();
+    }
+    
+    /**
+     * PostgreSQL 数据库
+     */
+    @Bean
+    @Profile("postgresql")
+    public DataSource postgresqlDataSource(
+            @Value("${DB_URL:jdbc:postgresql://localhost:5432/springboot_scaffold}") String url,
+            @Value("${DB_USER:postgres}") String username,
+            @Value("${DB_PASS:}") String password) {
+        log.info("🚀 使用 PostgreSQL 数据库: {}", url);
+        return DataSourceBuilder.create()
+            .driverClassName("org.postgresql.Driver")
+            .url(url)
+            .username(username)
+            .password(password)
+            .build();
+    }
+}

src/main/resources/application.properties

@@ -4,7 +4,7 @@ server.forward-headers-strategy=framework
 
 spring.profiles.active=${APP_PROFILE:learn}
 
-# H2 Database (default for learning)
+# H2 Database (default baseline; learn profile overrides to in-memory)
 spring.h2.console.enabled=true
 spring.datasource.url=jdbc:h2:file:~/h2/springboot_scaffold
 spring.datasource.driverClassName=org.h2.Driver