一.什么是AbstractWrapper
QueryWrapper(LambdaQueryWrapper) 和 UpdateWrapper(LambdaUpdateWrapper) 的父类
用于生成 sql 的 where 条件, entity 属性也用于生成 sql 的 where 条件
注意: entity 生成的 where 条件与 使用各个 api 生成的 where 条件没有任何关联行为

1.1wapper的关系继承图：

wapper介绍 ：
Wrapper ： 条件构造抽象类，最顶端父类，抽象类中提供4个方法西面贴源码展示
AbstractWrapper ： 用于查询条件封装，生成 sql 的 where 条件
AbstractLambdaWrapper ： Lambda 语法使用 Wrapper统一处理解析 lambda 获取 column。
LambdaQueryWrapper ：看名称也能明白就是用于Lambda语法使用的查询Wrapper
LambdaUpdateWrapper ： Lambda 更新封装Wrapper
QueryWrapper ： Entity 对象封装操作类，不是用lambda语法
UpdateWrapper ： Update 条件封装，用于Entity对象更新操作

二.方法解释
2.1 allEq
allEq(Map<R, V> params)
allEq(Map<R, V> params, boolean null2IsNull)
allEq(boolean condition, Map<R, V> params, boolean null2IsNull)
全部eq(或个别isNull)
个别参数说明:

params : key为数据库字段名,value为字段值
null2IsNull : 为true则在map的value为null时调用 isNull 方法,为false时则忽略value为null的

例1: allEq({id:1,name:“老王”,age:null})—>id = 1 and name = ‘老王’ and age is null
例2: allEq({id:1,name:“老王”,age:null}, false)—>id = 1 and name = ‘老王’
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)
个别参数说明:

filter : 过滤函数,是否允许字段传入比对条件中，说到底解释key里面要包含某个字符串比如下面“a”,name和age因为包含了a才能查询出来
params 与 null2IsNull : 同上

例1: allEq((k,v) -> k.indexOf(“a”) >= 0, {id:1,name:“老王”,age:null})—>name = ‘老王’ and age is null
例2: allEq((k,v) -> k.indexOf(“a”) >= 0, {id:1,name:“老王”,age:null}, false)—>name = ‘老王’
2.2eq
eq(R column, Object val)
eq(boolean condition, R column, Object val)
等于 =
例: eq(“name”, “老王”)—>name = ‘老王’
2.3ne
ne(R column, Object val)
ne(boolean condition, R column, Object val)
不等于 <>
例: ne(“name”, “老王”)—>name <> ‘老王’
2.4gt
gt(R column, Object val)
gt(boolean condition, R column, Object val)
大于 >
例: gt(“age”, 18)—>age > 18
2.5ge
ge(R column, Object val)
ge(boolean condition, R column, Object val)
大于等于 >=
例: ge(“age”, 18)—>age >= 18
2.6lt
lt(R column, Object val)
lt(boolean condition, R column, Object val)
小于 <
例: lt(“age”, 18)—>age < 18
2.7le
le(R column, Object val)
le(boolean condition, R column, Object val)
小于等于 <=
例: le(“age”, 18)—>age <= 18
2.8between
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
2.9notBetween
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
2.10like
like(R column, Object val)
like(boolean condition, R column, Object val)
LIKE ‘%值%’
例: like(“name”, “王”)—>name like ‘%王%’
2.11notLike
notLike(R column, Object val)
notLike(boolean condition, R column, Object val)
NOT LIKE ‘%值%’
例: notLike(“name”, “王”)—>name not like ‘%王%’
2.12likeLeft
likeLeft(R column, Object val)
likeLeft(boolean condition, R column, Object val)
LIKE ‘%值’
例: likeLeft(“name”, “王”)—>name like ‘%王’
2.13likeRight
likeRight(R column, Object val)
likeRight(boolean condition, R column, Object val)
LIKE ‘值%’
例: likeRight(“name”, “王”)—>name like ‘王%’
2.14isNull
isNull(R column)
isNull(boolean condition, R column)
字段 IS NULL
例: isNull(“name”)—>name is null
2.15isNotNull
isNotNull(R column)
isNotNull(boolean condition, R column)
字段 IS NOT NULL
例: isNotNull(“name”)—>name is not null
2.16in
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)
2.17notIn
notIn(R column, Collection<?> value) notIn(boolean condition, R column, Collection<?> value)
字段 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)
2.18inSql
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)
2.19notInSql
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”)—>age not in (select id from table where id < 3)
2.20groupBy
groupBy(R… columns)
groupBy(boolean condition, R… columns)
分组：GROUP BY 字段, …
例: groupBy(“id”, “name”)—>group by id,name
2.21orderByAsc
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
2.22orderByDesc
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
2.23orderBy
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
2.24having
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
2.25or
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 consumer)
or(boolean condition, Consumer consumer)
OR 嵌套
例: or(i -> i.eq(“name”, “李白”).ne(“status”, “活着”))—>or (name = ‘李白’ and status <> ‘活着’)
2.26and
and(Consumer consumer)
and(boolean condition, Consumer consumer)
AND 嵌套
例: and(i -> i.eq(“name”, “李白”).ne(“status”, “活着”))—>and (name = ‘李白’ and status <> ‘活着’)
2.27nested
nested(Consumer consumer)
nested(boolean condition, Consumer 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’)
2.28apply
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’”)
2.29last
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”)
2.30exists
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)
2.31notExists
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)
三.QueryWrapper
3.1select
select(String… sqlSelect)
select(Predicate predicate)
select(Class entityClass, Predicate predicate)
设置查询字段
说明:

以上方分法为两类.
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”))
四.UpdateWrapper
说明:

继承自 AbstractWrapper ,自身的内部属性 entity 也用于生成 where 条件
及 LambdaUpdateWrapper, 可以通过 new UpdateWrapper().lambda() 方法获取!

4.1set
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
4.2setSql
setSql(String sql)
设置 SET 部分 SQL
例: setSql(“name = ‘老李头’”)
4.3lambda
获取 LambdaWrapper
在QueryWrapper中是获取LambdaQueryWrapper
在UpdateWrapper中是获取LambdaUpdateWrapper
五.使用 Wrapper 自定义SQL
需求来源:

在使用了mybatis-plus之后, 自定义SQL的同时也想使用Wrapper的便利应该怎么办？ 在mybatis-plus版本3.0.7得到了完美解决 版本需要大于或等于3.0.7, 以下两种方案取其一即可

Service.java
mysqlMapper.getAll(Wrappers.lambdaQuery().eq(MysqlData::getGroup, 1));
方案一 注解方式 Mapper.java
@Select(“select * from mysql_data ${ew.customSqlSegment}”)
List getAll(@Param(Constants.WRAPPER) Wrapper wrapper);
方案二 XML形式 Mapper.xml

SELECT * FROM mysql_data ${ew.customSqlSegment}