mybatis-plus 实践

mybatis-plus 对原生 mybatis 做了扩展增强而不改变任何 mybatis 的原有逻辑, 安全可靠的同时极大降低了实体映射的代码量及配置量, 提升了程序员的工程效率!

ORM 配置

映射关系表达:

使用 @com.baomidou.mybatisplus.annotation.TableName 注解申明一个实体和一张数据库表的关系;
使用 @com.baomidou.mybatisplus.annotation.TableId 注解申明实体的字段与数据库表主键的关系;
使用 @com.baomidou.mybatisplus.annotation.TableField 注解申明实体的字段与数据库表字段的关系;

@TableName("t_xxx")
public class XXXDO {

    @TableId(value = "id", type = IdType.AUTO)
    private long id;

    @TableField("gmt_create")
    private Date gmtCreate;

    @TableField("gmt_modified")
    private Date gmtModified;

    @TableField("name")
    private String name;

    @TableField("type")
    private String type;

    @TableField("status")
    private String status;

    @TableField("version")
    private long version;

}

数据操纵

mybatis-plus 提供了功能强大的数据操纵方法, 在继承了 com.baomidou.mybatisplus.core.mapper.BaseMapper 后, 对于基础的增删改查, 几乎可以做到无需创建 mapper.xml 文件自己手写 sql 语句;
Mapper 接口只需继承 BaseMapper 即可:

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@org.apache.ibatis.annotations.Mapper
public interface XXXMapper extends BaseMapper<XXXDO> {
}

随后即可使用 BaseMapper 强大的数据操纵能力:
insert:

1	xxxMapper.insert(xxxDO);

select:

// select single
final LambdaQueryWrapper<XXXDO> queryWrapper = new LambdaQueryWrapper<>();
queryWrapper.eq(XXXDO::getName, name)
            .eq(XXXDO::getTenant, tenant);
final XXXDO xxxDO = xxxMapper.selectOne(queryWrapper);

// select list
final LambdaQueryWrapper<XXXDO> queryWrapper = new LambdaQueryWrapper<>();
queryWrapper.eq(XXXDO::getTag, tag)
            .eq(XXXDO::getTenant, tenant);
final List<XXXDO> xxxDOList = xxxMapper.selectList(queryWrapper);

update:

// update by condition
final LambdaUpdateWrapper<XXXDO> updateWrapper = new LambdaUpdateWrapper<>();
updateWrapper.set(XXXDO::getTags, ConvertUtil.commaJoin(tags))
             .eq(XXXDO::getName, name)
             .eq(XXXDO::getTenant, tenant);
return xxxMapper.update(null, updateWrapper);

// update by id
xxxMapper.updateById(xxxDO);

高级用法

动态表名处理

例如: 针对指定表的数据操纵, 统一为表名添加后缀;
此类场景可以使用 mybatis-plus 的 com.baomidou.mybatisplus.extension.plugins.handler.TableNameHandler 解决, 方案如下:
用于数据操纵中感知目标发布环境的工具:

@NoArgsConstructor(access = AccessLevel.PRIVATE)
public final class PublishEnvAwares {

    private static final ThreadLocal<Pair<String, Env>> publishEnvThreadLocal = new ThreadLocal<>();

    public static Pair<String, Env> getPublishEnvAwaredTableName() {
        return publishEnvThreadLocal.get();
    }

    /**
     * 在 procedure 过程中, 让 targetTableName 感知到目标发布环境 publishEnv
     */
    public static <T> T awarePublishEnv(Supplier<T> procedure, String targetTableName, Env publishEnv) {
        try {
            publishEnvThreadLocal.set(Pair.of(targetTableName, publishEnv));
            return procedure.get();
        } finally {
            publishEnvThreadLocal.remove();
        }
    }

}

基于目标发布环境的数据库表名动态计算扩展:

public class PublishEnvTableNameHandler implements TableNameHandler {

    private static final String TABLE_NAME_PUBLISH_ENV_JOINER = "_";

    @Override
    public String dynamicTableName(String sql, String tableName) {
        final Pair<String, Env> tableNameToPublishEnv = PublishEnvAwares.getPublishEnvAwaredTableName();
        if (tableNameToPublishEnv == null || !StringUtils.equals(tableNameToPublishEnv.getLeft(), tableName)) {
            return tableName;
        }
        return tableName + TABLE_NAME_PUBLISH_ENV_JOINER + tableNameToPublishEnv.getRight().getName();
    }

}

将动态表名处理器注册到 mybatis-plus:

@Configuration
public class MyBatisPlusConfig {

    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        final MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        // 新增分页拦截器, 并设置数据库类型为 mysql
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));

        // 表名动态计算
        final DynamicTableNameInnerInterceptor tableNameInterceptor = new DynamicTableNameInnerInterceptor();
        tableNameInterceptor.setTableNameHandler(new PublishEnvTableNameHandler());
        interceptor.addInnerInterceptor(tableNameInterceptor);
        return interceptor;
    }

}

实现表名后缀自动添加扩展的 Mapper:

@Mapper
public interface XXXMapper extends BaseMapper<XXXDO> {

    String TARGET_TABLE_NAME = "xxxx";

    default int insertWithPublishEnv(XXXDO xxxDO, Env publishEnv) {
        return PublishEnvAwares.awarePublishEnv(() -> this.insert(xxxDO),
                TARGET_TABLE_NAME, publishEnv);
    }

    default int updateByIdWithPublishEnv(@Param("et") XXXDO entity, Env publishEnv) {
        return PublishEnvAwares.awarePublishEnv(() -> this.updateById(entity),
                TARGET_TABLE_NAME, publishEnv);
    }

    default XXXDO selectWithPublishEnv(@Param("ew") Wrapper<XXXDO> queryWrapper,
                                               Env publishEnv) {
        return PublishEnvAwares.awarePublishEnv(() -> this.selectOne(queryWrapper),
                TARGET_TABLE_NAME, publishEnv);
    }

}

复杂查询语句

可以使用 LambdaQueryChainWrapper:

final LambdaQueryChainWrapper<XXXDO> queryWrapper = new LambdaQueryChainWrapper<>(xxxMapper);

final List<XXXDO> xxxDOList = queryWrapper.eq(XXXDO::getTenant, tenant)
        .eq(!ObjectUtils.isEmpty(type), XXXDO::getType, type)
        .apply(!CollectionUtils.isEmpty(devStatus), buildDevStatusPredicateSql(devStatus), devStatus)
        .apply(!CollectionUtils.isEmpty(tags), buildTagsPredicateSql(tags), tags)
        .apply(!CollectionUtils.isEmpty(nameSegments), buildNamePredicateSql(nameSegments), nameSegments)
        .in(XXXDO::getApp, appCodes)
        .orderBy(order != null, Order.isAsc(order), XXXDO::getGmtModified)
        .last(String.format("limit %d,%d", (pageNum - 1) * pageSize, pageSize));
        .list();
        
/**
 * @return e.g. name LIKE '%com.api.name%1%'
 */
private String buildNamePredicateSql(List<String> nameSegments) {
    return "name LIKE '" + nameSegments.stream().collect(Collectors.joining("%", "%", "%")) + "'";
}

/**
 * @return e.g. dev_status ->> '$.DAILY' = 'UNPUBLISHED' AND  dev_status ->> '$.PRE' = 'UNPUBLISHED' AND  dev_status ->> '$.PROD' = 'UNPUBLISHED'
*/
private static String buildDevStatusPredicateSql(Map<Env, DevStatus> devStatus) {
    if (CollectionUtils.isEmpty(devStatus)) {
        return EMPTY_STRING;
    }
    return devStatus.entrySet().stream().map(envDevStatusEntry -> "devStatus ->> '$." + envDevStatusEntry.getKey() + "' = '" + envDevStatusEntry.getValue() + "'")
            .collect(Collectors.joining(" AND "));
}

/**
 * @return e.g. tags LIKE '%tag1% OR %tag2%'
 */
private static String buildTagsPredicateSql(Set<String> tags) {
    if (CollectionUtils.isEmpty(tags)) {
        return EMPTY_STRING;
    }
    return tags.stream().map(tag -> "tags LIKE '%" + tag + "%'")
            .collect(Collectors.joining(" OR "));
}

参考链接

MyBatis-Plus