MyBatis-Plus

https://mybatis.plus/
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MyBatis-Plus is an enhanced ORM framework built on MyBatis that simplifies database operations with...
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### Spring Boot MyBatis-Plus Configuration

Source: https://mybatis.plus/config

Example of MyBatis-Plus configuration in a Spring Boot application using application.properties or application.yml.

```yaml
mybatis-plus:
  ......
  configuration:
    ......
  global-config:
    ......
    db-config:
      ......  

```

--------------------------------

### Spring MVC MyBatis-Plus Configuration

Source: https://mybatis.plus/config

Example of configuring MyBatis-Plus in a Spring MVC application using XML bean definitions.

```xml
<bean id="sqlSessionFactory" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
    <property name="configuration" ref="configuration"/> <!--  非必须  -->
    <property name="globalConfig" ref="globalConfig"/> <!--  非必须  -->
    ......
</bean>

<bean id="configuration" class="com.baomidou.mybatisplus.core.MybatisConfiguration">
    ......
</bean>

<bean id="globalConfig" class="com.baomidou.mybatisplus.core.config.GlobalConfig">
    <property name="dbConfig" ref="dbConfig"/> <!--  非必须  -->
    ......
</bean>

<bean id="dbConfig" class="com.baomidou.mybatisplus.core.config.GlobalConfig.DbConfig">
    ......
</bean>

```

--------------------------------

### MyBatis-Plus Global Configuration

Source: https://mybatis.plus/guide/building-the-database-layer-of-a-high-concurrency-online-gambling-platform-using-mybatis-plus

Configures MyBatis-Plus interceptors for features like optimistic locking and pagination. This setup is essential for enabling these functionalities across the application.

```java
 @Configuration public class MybatisPlusConfig { @Bean public MybatisPlusInterceptor interceptor() { MybatisPlusInterceptor i = new MybatisPlusInterceptor(); i.addInnerInterceptor(new OptimisticLockerInnerInterceptor()); // 乐观锁 i.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL)); // 分页 return i; } } 
```

--------------------------------

### Provide Encryption Key via Jar Startup Argument

Source: https://mybatis.plus/guide/safety.html

Pass the encryption key as a startup argument to your Jar file using the '--mpw.key=' format. This can also be set as a startup environment variable on servers.

```bash
--mpw.key=d1104d7c3b616f0b
```

--------------------------------

### Configure p6spy Datasource in application.yml

Source: https://mybatis.plus/guide/p6spy.html

Set the datasource driver class name and URL to use p6spy for logging SQL statements.

```yaml
spring:
  datasource:
    driver-class-name: com.p6spy.engine.spy.P6SpyDriver
    url: jdbc:p6spy:h2:mem:test
    ...
```

--------------------------------

### XML Mapper for Custom Pagination Method

Source: https://mybatis.plus/guide/interceptor-pagination.html

The XML mapper configuration for a custom pagination method. Ensure the SQL query selects the necessary fields.

```xml
<select id="selectPageVo" resultType="com.baomidou.cloud.entity.UserVo">
    SELECT id,name FROM user WHERE state=#{state}
</select>
```

--------------------------------

### Configure spy.properties for p6spy

Source: https://mybatis.plus/guide/p6spy.html

Customize p6spy logging behavior, including module list, log format, appender, and exclusion categories.

```properties
#3.2.1以上使用
modulelist=com.baomidou.mybatisplus.extension.p6spy.MybatisPlusLogFactory,com.p6spy.engine.outage.P6OutageFactory
#3.2.1以下使用或者不配置
#modulelist=com.p6spy.engine.logging.P6LogFactory,com.p6spy.engine.outage.P6OutageFactory
# 自定义日志打印
logMessageFormat=com.baomidou.mybatisplus.extension.p6spy.P6SpyLogger
#日志输出到控制台
appender=com.baomidou.mybatisplus.extension.p6spy.StdoutLogger
# 使用日志系统记录 sql
#appender=com.p6spy.engine.spy.appender.Slf4JLogger
# 设置 p6spy driver 代理
deregisterdrivers=true
# 取消JDBC URL前缀
useprefix=true
# 配置记录 Log 例外,可去掉的结果集有error,info,batch,debug,statement,commit,rollback,result,resultset.
excludecategories=info,debug,result,commit,resultset
# 日期格式
dateformat=yyyy-MM-dd HH:mm:ss
# 实际驱动可多个
#driverlist=org.h2.Driver
# 是否开启慢SQL记录
outagedetection=true
# 慢SQL记录标准 2 秒
outagedetectioninterval=2
```

--------------------------------

### Generate and Use AES Key for Encryption

Source: https://mybatis.plus/guide/safety.html

Generate a 16-bit random AES key using AES.generateRandomKey() and then use AES.encrypt() to encrypt your data. The generated random key must be securely managed.

```java
// Generate 16位随机AES密钥
String randomKey = AES.generateRandomKey();

// 随机密钥加密
String result = AES.encrypt(data, randomKey);

```

--------------------------------

### Configure Encrypted Database Credentials in YML

Source: https://mybatis.plus/guide/safety.html

Use the 'mpw:' prefix for encrypted values in your YML configuration for database URL, password, and username. Ensure the key used for encryption is kept secure.

```yaml
spring:
  datasource:
    url: mpw:qRhvCwF4GOqjessEB3G+a5okP+uXXr96wcucn2Pev6Bf1oEMZ1gVpPPhdDmjQqoM
    password: mpw:Hzy5iliJbwDHhjLs1L0j6w==
    username: mpw:Xb+EgsyuYRXw7U7sBJjBpA==
```

--------------------------------

### Mybatis-config.xml Configuration for MybatisPlusInterceptor

Source: https://mybatis.plus/guide/interceptor.html

Configure MybatisPlusInterceptor with PaginationInnerInterceptor in mybatis-config.xml.

```xml
<plugins>
  <plugin interceptor="com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor">
    <property name="@page" value="com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor"/>
    <property name="page:dbType" value="h2"/>
  </plugin>
</plugins>
```

--------------------------------

### Add p6spy Gradle Dependency

Source: https://mybatis.plus/guide/p6spy.html

Include the p6spy dependency in your Gradle project to enable SQL logging.

```gradle
compile group: 'p6spy', name: 'p6spy', version: '最新版本'
```

--------------------------------

### MyBatis Configuration - Auto Mapping Unknown Column Behavior

Source: https://mybatis.plus/config

Specifies how MyBatis handles unknown columns or properties during automatic mapping. Options include NONE (no action), WARNING (log warnings), and FAILING (throw an exception).

```properties
autoMappingUnknownColumnBehavior=NONE
```

--------------------------------

### Add p6spy Maven Dependency

Source: https://mybatis.plus/guide/p6spy.html

Include the p6spy dependency in your Maven project to enable SQL logging.

```xml
<dependency>
  <groupId>p6spy</groupId>
  <artifactId>p6spy</artifactId>
  <version>最新版本</version>
</dependency>
```

--------------------------------

### Paginated Query Template in MyBatis-Plus

Source: https://mybatis.plus/guide/building-the-database-layer-of-a-high-concurrency-online-gambling-platform-using-mybatis-plus

Provides a template for performing paginated queries using MyBatis-Plus's lambda query builder. It includes ordering and avoids deep pagination issues by using standard page parameters.

```java
 public IPage<BetOrder> pageOrders(Long userId, long pageNo, long pageSize) { Page<BetOrder> p = new Page<>(pageNo, pageSize); return lambdaQuery() .eq(BetOrder::getUserId, userId) .orderByDesc(BetOrder::getCreatedAt) .page(p); } 
```

--------------------------------

### Spring Boot Configuration for MybatisPlusInterceptor

Source: https://mybatis.plus/guide/interceptor.html

Configure MybatisPlusInterceptor with PaginationInnerInterceptor in a Spring Boot application using Java configuration.

```java
@Configuration
@MapperScan("scan.your.mapper.package")
public class MybatisPlusConfig {

    /**
     * 新的分页插件,一缓和二缓遵循mybatis的规则,需要设置 MybatisConfiguration#useDeprecatedExecutor = false 避免缓存出现问题(该属性会在旧插件移除后一同移除)
     */
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.H2));
        return interceptor;
    }

    @Bean
    public ConfigurationCustomizer configurationCustomizer() {
        return configuration -> configuration.setUseDeprecatedExecutor(false);
    }
}
```

--------------------------------

### Configure BlockAttackSqlParser in PaginationInterceptor

Source: https://mybatis.plus/guide/block-attack-sql-parser.html

Add BlockAttackSqlParser to the sqlParserList within PaginationInterceptor to enable protection against malicious SQL. You can customize the parser to exempt specific tables from these protections.

```java
@Bean
public PaginationInterceptor paginationInterceptor() {
    PaginationInterceptor paginationInterceptor = new PaginationInterceptor();

    ... 

    List<ISqlParser> sqlParserList = new ArrayList<>();
    // 攻击 SQL 阻断解析器、加入解析链
    sqlParserList.add(new BlockAttackSqlParser() {
            @Override
            public void processDelete(Delete delete) {
                // 如果你想自定义做点什么，可以重写父类方法像这样子
                if ("user".equals(delete.getTable().getName())) {
                    // 自定义跳过某个表，其他关联表可以调用 delete.getTables() 判断
                    return ;
                }
                super.processDelete(delete);
            }
        });
    paginationInterceptor.setSqlParserList(sqlParserList);

    ... 

    return paginationInterceptor;
}
```

--------------------------------

### Custom Mapper Method for Pagination

Source: https://mybatis.plus/guide/interceptor-pagination.html

Define custom mapper methods to handle pagination. The return type (IPage or List) dictates how the pagination parameters are handled and how results are set.

```java
IPage<User> selectPageVo(IPage<?> page, Integer state);
// or
List<User> selectPageVo(IPage<User> page, Integer state);
```

--------------------------------

### TenantLineHandler Interface Definition

Source: https://mybatis.plus/guide/interceptor-tenant-line.html

Defines the contract for handling tenant-specific logic, including retrieving tenant IDs, specifying tenant columns, and ignoring specific tables.

```java
public interface TenantLineHandler {

    /**
     * 获取租户 ID 值表达式，只支持单个 ID 值
     * <p>
     *
     * @return 租户 ID 值表达式
     */
    Expression getTenantId();

    /**
     * 获取租户字段名
     * <p>
     * 默认字段名叫: tenant_id
     *
     * @return 租户字段名
     */
    default String getTenantIdColumn() {
        return "tenant_id";
    }

    /**
     * 根据表名判断是否忽略拼接多租户条件
     * <p>
     * 默认都要进行解析并拼接多租户条件
     *
     * @param tableName 表名
     * @return 是否忽略, true:表示忽略，false:需要解析并拼接多租户条件
     */
    default boolean ignoreTable(String tableName) {
        return false;
    }
}
```

--------------------------------

### Spring MVC Configuration for MybatisPlusInterceptor

Source: https://mybatis.plus/guide/interceptor.html

Configure MybatisPlusInterceptor with PaginationInnerInterceptor in a Spring MVC application using XML beans.

```xml
<bean id="sqlSessionFactory" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
    <!-- 其他属性 略 --> 
    <property name="configuration" ref="configuration"/>
    <property name="plugins">
        <array>
            <ref bean="mybatisPlusInterceptor"/>
        </array>
    </property>
</bean>

<bean id="configuration" class="com.baomidou.mybatisplus.core.MybatisConfiguration">
    <!-- 需配置该值为false,避免1或2级缓存可能出现问题,该属性会在旧插件移除后一同移除 -->
    <property name="useDeprecatedExecutor" value="false"/>
</bean>

<bean id="mybatisPlusInterceptor" class="com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor">
    <property name="interceptors">
        <list>
            <ref bean="paginationInnerInterceptor"/>
        </list>
    </property>
</bean>

<bean id="paginationInnerInterceptor" class="com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor">
    <!-- 对于单一数据库类型来说,都建议配置该值,避免每次分页都去抓取数据库类型 -->
    <constructor-arg name="dbType" value="H2"/>
</bean>
```

--------------------------------

### MyBatis Configuration - Auto Mapping Behavior

Source: https://mybatis.plus/config

Defines MyBatis's automatic mapping strategy for data table fields to object properties. Options are NONE (no auto-mapping), PARTIAL (auto-mapping for non-nested results), and FULL (auto-mapping for all results).

```properties
autoMappingBehavior=PARTIAL
```

--------------------------------

### MyBatis Configuration - Cache Enabled

Source: https://mybatis.plus/config

Enables or disables MyBatis's second-level cache. Defaults to true.

```properties
cacheEnabled=true
```

--------------------------------

### MyBatis Configuration - Map Underscore to Camel Case

Source: https://mybatis.plus/config

Enables automatic mapping between database column names (snake_case) and Java property names (camelCase). This setting also affects SQL select statements generated by MyBatis-Plus.

```properties
mapUnderscoreToCamelCase=true
```

--------------------------------

### Settlement and Cache Invalidation

Source: https://mybatis.plus/guide/building-the-database-layer-of-a-high-concurrency-online-gambling-platform-using-mybatis-plus

Handles the settlement process, including database updates and subsequent cache invalidation for related data. Ensures that stale data is not served after settlement.

```java
 @Transactional public boolean settleAndInvalidate(Long orderId) { boolean ok = settlementService.doSettle(orderId); // 结算落库 if (ok) { redis.del("ORDER_DETAIL:" + orderId); redis.del("ORDER_LIST:" + getUserIdByOrder(orderId)); } return ok; } 
```

--------------------------------

### MyBatis Configuration - Aggressive Lazy Loading

Source: https://mybatis.plus/config

When enabled, lazy-loaded objects may have all their lazy properties loaded at once. This setting requires `lazyLoadingEnabled` to be active.

```properties
aggressiveLazyLoading=true
```

--------------------------------

### Optimistic Locking with Retries in MyBatis-Plus

Source: https://mybatis.plus/guide/building-the-database-layer-of-a-high-concurrency-online-gambling-platform-using-mybatis-plus

Handles concurrent updates to critical resources like wallet balances by implementing optimistic locking with a version field. Includes a retry mechanism with random backoff for failed updates due to version conflicts.

```java
 @Transactional public boolean debitWithRetry(Long userId, BigDecimal amount) { for (int i = 0; i < 3; i++) { Wallet w = lambdaQuery().eq(Wallet::getUserId, userId).one(); if (w == null || w.getBalance().compareTo(amount) < 0) return false; w.setBalance(w.getBalance().subtract(amount)); if (updateById(w)) return true; // version 命中即成功 try { Thread.sleep(20L * (i + 1)); } catch (InterruptedException ignored) {} } return false; } 
```

--------------------------------

### Cache Invalidation After Database Write

Source: https://mybatis.plus/guide/building-the-database-layer-of-a-high-concurrency-online-gambling-platform-using-mybatis-plus

Demonstrates invalidating relevant Redis caches after a successful database write operation to maintain data consistency. This is crucial for scenarios requiring strong consistency.

```java
 // 写库成功后删缓存（键名示例：ORDER_LIST:userId） @Transactional public void createOrderAndInvalidateCache(BetOrder req) { save(req); // DB 写入 redis.del("ORDER_LIST:" + req.getUserId()); // 失效相关缓存 } 
```

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### MyBatis Configuration - Local Cache Scope

Source: https://mybatis.plus/config

Configures the scope of MyBatis's first-level cache. SESSION (default) caches within a session, while STATEMENT disables the cache for each statement.

```properties
localCacheScope=SESSION
```

--------------------------------

### MyBatis Configuration - Default Enum Type Handler

Source: https://mybatis.plus/config

Specifies the default TypeHandler for enums. Options include storing enum names, ordinal values, or using custom handlers for enums implementing IEnum or marked with @EnumValue.

```properties
defaultEnumTypeHandler=org.apache.ibatis.type.EnumTypeHandler
```
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