对list查询后的结果用Stream流进行了一些封装，使其可以返回一些指定结果，简洁了api的调用,这种调用方式不用注入bean、不用注入bean、不用注入bean，通过实体类class查询
**SimpleQuery.list()、SimpleQuery.keyMap()**较常用
<!--低版本没有这个工具类-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.5.1</version>
</dependency>// 获取ID
List<Long> list = SimpleQuery.list(new QueryWrapper<HssTypePropertyEntity>()
.eq("type_id",5).lambda(), HssTypePropertyEntity::getId);
// 以typeId为key分组
Map<Long, HssEquipmentEntity> map =
SimpleQuery.keyMap(new QueryWrapper<HssEquipmentEntity>()
.eq("type_id", 5).lambda(),
HssEquipmentEntity::getTypeId);
// 查询角色的隐藏ID，以角色ID分组
Map<Long, List<Long>> columnMap =
SimpleQuery.group(new QueryWrapper<SysRoleColumnEntity>().lambda(),
SysRoleColumnEntity::getRoleId,
Collectors.mapping(SysRoleColumnEntity::getColumnId, Collectors.toList()));操作实例：
// 我要这个表里对应条件的用户，用id作为key给我一个map
Map<Long, Entity> idEntityMap = SimpleQuery.keyMap(Wrappers.<Entity>lambdaQuery().eq(Entity::getId, 1L), Entity::getId);
// 校验结果
Entity entity = new Entity();
entity.setId(1L);
entity.setName("ruben");
Assert.isTrue(idEntityMap.equals(Collections.singletonMap(1L, entity)), "Ops!");
// 如果我只想要id和name组成的map
Map<Long, String> idNameMap = SimpleQuery.map(Wrappers.lambdaQuery(), Entity::getId, Entity::getName);
// 校验结果
Map<Long, String> map = new HashMap<>(1 << 2);
map.put(1L, "ruben");
map.put(2L, null);
Assert.isTrue(idNameMap.equals(map), "Ops!");
}
@Test
public void testGroup() {
// 我需要相同名字的用户的分为一组，再造一条数据
doTestAutoCommit(m -> {
Entity entity = new Entity();
entity.setId(3L);
entity.setName("ruben");
m.insert(entity);
});
// 简单查询
Map<String, List<Entity>> nameUsersMap = SimpleQuery.group(Wrappers.lambdaQuery(), Entity::getName);
// 校验结果
Map<String, List<Entity>> map = new HashMap<>(1 << 2);
Entity chao = new Entity();
chao.setId(2L);
chao.setName(null);
map.put(null, Collections.singletonList(chao));
Entity ruben = new Entity();
ruben.setId(1L);
ruben.setName("ruben");
Entity ruben2 = new Entity();
ruben2.setId(3L);
ruben2.setName("ruben");
map.put("ruben", Arrays.asList(ruben, ruben2));
Assert.isTrue(nameUsersMap.equals(map), "Ops!");
// 解锁高级玩法：
// 获取Map<name,List<id>>
Map<String, List<Long>> nameIdMap = SimpleQuery.group(Wrappers.lambdaQuery(), Entity::getName, Collectors.mapping(Entity::getId, Collectors.toList()));
// 获取Map<name,个数>
Map<String, Long> nameCountMap = SimpleQuery.group(Wrappers.lambdaQuery(), Entity::getName, Collectors.counting());
// ...超多花样
}
@Override
protected String tableDataSql() {
return "insert into entity(id,name) values(1,'ruben'),(2,null);";
}
@Override
protected List<String> tableSql() {
return Arrays.asList("drop table if exists entity", "CREATE TABLE IF NOT EXISTS entity (" +
"id BIGINT NOT NULL," +
"name VARCHAR(30) NULL DEFAULT NULL," +
"PRIMARY KEY (id))");
}当然原来的查询也可以，只是还需要注入bean才能操作，listObjs(wrapper,mapper)
List<Long> strings =
hssTypePropertyService.listObjs(new QueryWrapper<HssTypePropertyEntity>()
.select("id").eq("type_id", 5)
,i->Long.valueOf(i.toString()));
ActiveRecord (查询)模式
说明:
实体继承 Model，调用自mapper，省去注入！
@Data
@TableName(value = "hss_history", autoResultMap = true)
public class HssHistoryEntity extends Model<HssHistoryEntity> implements Serializable {
private static final long serialVersionUID = 1L;
@TableId
private Long id;
// json映射，autoResultMap必须开启，写了xml查询需要resultMap映射字段
//查询映射<result column="data" property="data" typeHandler="com.baomidou.mybatisplus.extension.handlers.JacksonTypeHandler" javaType="com.alibaba.fastjson.JSONObject"/>
//更新映射#{e.data,jdbcType=VARCHAR,typeHandler=com.baomidou.mybatisplus.extension.handlers.JacksonTypeHandler},
@TableField(typeHandler = JacksonTypeHandler.class)
private JSONObject data;
}
创建对象直接就可以使用crud，省去注入
HssHistoryEntity entity = new HssHistoryEntity(); // 创建对象直接就有crud了 entity.insert(); entity.selectList(new QueryWrapper<HssHistoryEntity>()); entity.updateById(); entity.deleteById();
