MyBatis-Plus条件构造器入门学习

MyBatis-Plus条件构造器入门学习

官网：https://baomidou.com/pages/10c804/#abstractwrapper

AbstractWrapper

是QueryWrapper(LambdaQueryWrapper) 和UpdateWrapper(LambdaUpdateWrapper) 的父类。

PS:入参boolean condition表示该条件是否加入最后生成的sql中，例如：query.like(StringUtils.isNotBlank(name), Entity::getName, name) .eq(age!=null && age >= 0, Entity::getAge, age)

allEq

方法：

allEq(Map<R, V> params)
allEq(Map<R, V> params, boolean null2IsNull)
allEq(boolean condition, Map<R, V> params, boolean null2IsNull)
allEq(BiPredicate<R, V> filter, Map<R, V> params)
allEq(BiPredicate<R, V> filter, Map<R, V> params, boolean null2IsNull)
allEq(boolean condition, BiPredicate<R, V> filter, Map<R, V> params, boolean null2IsNull)

使用实例：

Map map=new HashMap();
map.put("name","周杰伦9");
map.put("age",null);

//方法对应生成的sql
wrapper.allEq(map);//allEq({name:"周杰伦9",age:null})---> name = '周杰伦9' and age is null
wrapper.allEq(map,false);//allEq({name:"周杰伦9",age:null})---> name = '周杰伦9'

//filter : 过滤函数,是否允许字段传入比对条件中
wrapper.allEq((k,v) -> k.indexOf("a") >= 0,map,false);//allEq({name:"周杰伦9",age:null})---> name = '周杰伦9'

eq

eq(R column, Object val)
eq(boolean condition, R column, Object val)
  • 等于 =
  • 例: eq("name", "老王")—>name = '老王'

gt

gt(R column, Object val)
gt(boolean condition, R column, Object val)
  • 大于 >
  • 例: gt("age", 18)—>age > 18

ge

ge(R column, Object val)
ge(boolean condition, R column, Object val)
  • 大于等于 >=
  • 例: ge("age", 18)—>age >= 18

lt

lt(R column, Object val)
lt(boolean condition, R column, Object val)
  • 小于 <
  • 例: lt("age", 18)—>age < 18

le

le(R column, Object val)
le(boolean condition, R column, Object val)
  • 小于等于 <=
  • 例: le("age", 18)—>age <= 18

between

between(R column, Object val1, Object val2)
between(boolean condition, R column, Object val1, Object val2)
  • BETWEEN 值1 AND 值2
  • 例: between("age", 18, 30)—>age between 18 and 30

notBetween

notBetween(R column, Object val1, Object val2)
notBetween(boolean condition, R column, Object val1, Object val2)
  • NOT BETWEEN 值1 AND 值2
  • 例: notBetween("age", 18, 30)—>age not between 18 and 30

like

like(R column, Object val)
like(boolean condition, R column, Object val)
  • LIKE ‘%值%’
  • 例: like("name", "王")—>name like '%王%'

notLike

notLike(R column, Object val)
notLike(boolean condition, R column, Object val)
  • NOT LIKE ‘%值%’
  • 例: notLike("name", "王")—>name not like '%王%'

likeLeft

likeLeft(R column, Object val)
likeLeft(boolean condition, R column, Object val)
  • LIKE ‘%值’
  • 例: likeLeft("name", "王")—>name like '%王'

likeRight

likeRight(R column, Object val)
likeRight(boolean condition, R column, Object val)
  • LIKE ‘值%’
  • 例: likeRight("name", "王")—>name like '王%'

isNull

isNull(R column)
isNull(boolean condition, R column)
  • 字段 IS NULL
  • 例: isNull("name")—>name is null

isNotNull

isNotNull(R column)
isNotNull(boolean condition, R column)
  • 字段 IS NOT NULL
  • 例: isNotNull("name")—>name is not null

in

in(R column, Collection<?> value)
in(boolean condition, R column, Collection<?> value)
  • 字段 IN (value.get(0), value.get(1), …)
  • 例: in("age",{1,2,3})—>age in (1,2,3)
in(R column, Object... values)
in(boolean condition, R column, Object... values)
  • 字段 IN (v0, v1, …)
  • 例: in("age", 1, 2, 3)—>age in (1,2,3)

可传Collection集合，也可以直接传多个参数

List ages=new ArrayList();
ages.add(18);
ages.add(16);
ages.add(15);

wrapper.in("age",ages);
wrapper.in("age",15,0,1);

在这里插入图片描述

notIn

notIn(R column, Collection<?> value)
notIn(boolean condition, R column, Collection<?> value)
  • 字段 NOT IN (value.get(0), value.get(1), …)
  • 例: notIn("age",{1,2,3})—>age not in (1,2,3)
notIn(R column, Object... values)
notIn(boolean condition, R column, Object... values)
  • 字段 NOT IN (v0, v1, …)
  • 例: notIn("age", 1, 2, 3)—>age not in (1,2,3)

inSql

inSql(R column, String inValue)
inSql(boolean condition, R column, String inValue)
  • 字段 IN ( sql语句 )
  • 例: inSql("age", "1,2,3,4,5,6")—>age in (1,2,3,4,5,6)
  • 例: inSql("id", "select id from table where id < 3")—>id in (select id from table where id < 3)

notInSql

notInSql(R column, String inValue)
notInSql(boolean condition, R column, String inValue)
  • 字段 NOT IN ( sql语句 )
  • 例: notInSql("age", "1,2,3,4,5,6")—>age not in (1,2,3,4,5,6)
  • 例: notInSql("id", "select id from table where id < 3")—>id not in (select id from table where id < 3)

groupBy

groupBy(R... columns)
groupBy(boolean condition, R... columns)
  • 分组：GROUP BY 字段, …
  • 例: groupBy("id", "name")—>group by id,name

orderByAsc

orderByAsc(R... columns)
orderByAsc(boolean condition, R... columns)
  • 排序：ORDER BY 字段, … ASC
  • 例: orderByAsc("id", "name")—>order by id ASC,name ASC

orderByDesc

orderByDesc(R... columns)
orderByDesc(boolean condition, R... columns)
  • 排序：ORDER BY 字段, … DESC
  • 例: orderByDesc("id", "name")—>order by id DESC,name DESC

orderBy

orderBy(boolean condition, boolean isAsc, R... columns)
  • 排序：ORDER BY 字段, …
  • 例: orderBy(true, true, "id", "name")—>order by id ASC,name ASC

having

having(String sqlHaving, Object... params)
having(boolean condition, String sqlHaving, Object... params)
  • HAVING ( sql语句 )
  • 例: having("sum(age) > 10")—>having sum(age) > 10
  • 例: having("sum(age) > {0}", 11)—>having sum(age) > 11

演示：

wrapper.groupBy("id").having("sum(age)>10");

在这里插入图片描述

func

func(Consumer<Children> consumer)
func(boolean condition, Consumer<Children> consumer)
  • func 方法(主要方便在出现if…else下调用不同方法能不断链)
  • 例: func(i -> if(true) {i.eq("id", 1)} else {i.ne("id", 1)})

or

or()
or(boolean condition)

  • 拼接 OR

    注意事项:

    主动调用or表示紧接着下一个方法不是用and连接!(不调用or则默认为使用and连接)

  • 例: eq("id",1).or().eq("name","老王")—>id = 1 or name = '老王'

or(Consumer<Param> consumer)
or(boolean condition, Consumer<Param> consumer)
  • OR 嵌套
  • 例: or(i -> i.eq("name", "李白").ne("status", "活着"))—>or (name = '李白' and status <> '活着')

and

and(Consumer<Param> consumer)
and(boolean condition, Consumer<Param> consumer)
  • AND 嵌套
  • 例: and(i -> i.eq("name", "李白").ne("status", "活着"))—>and (name = '李白' and status <> '活着')

nested

nested(Consumer<Param> consumer)
nested(boolean condition, Consumer<Param> consumer)
  • 正常嵌套 不带 AND 或者 OR
  • 例: nested(i -> i.eq("name", "李白").ne("status", "活着"))—>(name = '李白' and status <> '活着')

apply

apply(String applySql, Object... params)
apply(boolean condition, String applySql, Object... params)

  • 拼接 sql

    注意事项:

    该方法可用于数据库函数 动态入参的params对应前面applySql内部的{index}部分.这样是不会有sql注入风险的,反之会有!

  • 例: apply("id = 1")—>id = 1

  • 例: apply("date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")—>date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")

  • 例: apply("date_format(dateColumn,'%Y-%m-%d') = {0}", "2008-08-08")—>date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")

有什么特别的sql语句直接用apply拼接就行

last

last(String lastSql)
last(boolean condition, String lastSql)

  • 无视优化规则直接拼接到 sql 的最后

    注意事项:

    只能调用一次,多次调用以最后一次为准 有sql注入的风险,请谨慎使用

  • 例: last("limit 1")

exists

exists(String existsSql)
exists(boolean condition, String existsSql)
  • 拼接 EXISTS ( sql语句 )
  • 例: exists("select id from table where age = 1")—>exists (select id from table where age = 1)

notExists

notExists(String notExistsSql)
notExists(boolean condition, String notExistsSql)
  • 拼接 NOT EXISTS ( sql语句 )
  • 例: notExists("select id from table where age = 1")—>not exists (select id from table where age = 1)

QueryWrapper

select

select(String... sqlSelect)
select(Predicate<TableFieldInfo> predicate)
select(Class<T> entityClass, Predicate<TableFieldInfo> predicate)

  • 设置查询字段

    说明:

    以上方法分为两类.
    第二类方法为:过滤查询字段(主键除外),入参不包含 class 的调用前需要wrapper内的entity属性有值! 这两类方法重复调用以最后一次为准

  • 例: select("id", "name", "age")

  • 例: select(i -> i.getProperty().startsWith("test"))

UpdateWrapper

set

set(String column, Object val)
set(boolean condition, String column, Object val)
  • SQL SET 字段
  • 例: set("name", "老李头")
  • 例: set("name", "")—>数据库字段值变为空字符串
  • 例: set("name", null)—>数据库字段值变为null

setSql

setSql(String sql)
  • 设置 SET 部分 SQL
  • 例: setSql("name = '老李头'")

lambda

  • 获取 LambdaWrapper
    在QueryWrapper中是获取LambdaQueryWrapper
    在UpdateWrapper中是获取LambdaUpdateWrapper

链式调用 lambda 式

// 区分:
// 链式调用 普通
UpdateChainWrapper<T> update();
// 链式调用 lambda 式。注意：不支持 Kotlin 
LambdaUpdateChainWrapper<T> lambdaUpdate();

// 等价示例：
query().eq("id", value).one();
lambdaQuery().eq(Entity::getId, value).one();

// 等价示例：
update().eq("id", value).remove();
lambdaUpdate().eq(Entity::getId, value).remove();