20191209-mybatisplus（二） 条件构造器
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
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 !!!
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Mybatis-Plus 通过 QueryWrapper（MP封装的一个查询条件构造器，继承自AbstractWrapper，AbstractWrapper实现了 Wrapper等接口)来让用户自由的构建查询条件，简单便捷，没有额外的负担，能够有效提高开发效率
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查询包装器QueryWrapper， 主要用于处理 sql 拼接，排序，实体参数查询等
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注意: 使用的是 数据库字段 ，不是 Java 属性!
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需要这些功能时，只需要创建 QueryWrapper对象 即可
模糊查询
- like ===> %值% ==> queryWrapper.like(数据库中的列名,查询条件)
- .lt <小于
@Test
public void selectByWrapper(){
QueryWrapper queryWrapper=new QueryWrapper();
QueryWrapper query= Wrappers.query();
queryWrapper.like("name","雨").lt("age",40);
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
=> SELECT id,create_time,name,manager_id,email,age FROM user WHERE (name LIKE ‘%雨%’ AND age < 40)
- isNotNull 字段 IS NOT NULL
- between (R column, Object val1, Object val2)==> BETWEEN 值1 AND 值2
@Test
public void selectByWrapper2(){
QueryWrapper queryWrapper=new QueryWrapper();
queryWrapper.like("name","雨").between("age",20,40).isNotNull("email");
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
=> SELECT id,create_time,name,manager_id,email,age FROM user WHERE (name LIKE ‘%雨%’ AND age BETWEEN 20 AND 40 AND email IS NOT NULL)
- orderByAsc (R… columns) 升序
- orderByDesc (R… columns) 降序
- likeRight (R column, Object val) ==> LIKE ‘值%’
名字为王姓或者年龄大于等于25，按照年龄降序排列，年龄相同按照id升序排列
@Test
public void selectByWrapper3(){
QueryWrapper queryWrapper=new QueryWrapper();
queryWrapper.likeRight("name","王").or().ge("age",25).orderByDesc("age")
.orderByAsc("id");
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
=> SELECT id,create_time,name,manager_id,email,age FROM user WHERE (name LIKE 王% OR age >= 25) ORDER BY age DESC , id ASC
嵌套查询
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inSql (R column, String inValue)==>字段 IN ( sql语句 )
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apply (String applySql, Object… params)==>拼接 sql
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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!
第一种方式:存在sql语句注入的风险 建议不要使用该方式
queryWrapper.apply("date_format(create_time,'%Y-%m-%d')='2019-02-14'")
==》SELECT id,create_time,name,manager_id,email,age FROM user WHERE (date_format(create_time,'%Y-%m-%d')='2019-02-14'
queryWrapper.apply("date_format(create_time,'%Y-%m-%d')={0}","2019-02-14")
==> SELECT id,create_time,name,manager_id,email,age FROM user WHERE (date_format(create_time,'%Y-%m-%d')=?
创建日期为2019年2月14日并且直属上级为名字为王姓
date_format(create_time,'%Y-%m-%d')='2019-02-14' and manager_id in (select id from user where name like '王%')
@Test
public void selectByWrapper4(){
QueryWrapper queryWrapper=new QueryWrapper();
queryWrapper.apply("date_format(create_time,'%Y-%m-%d')={0}","2019-02-14")
.inSql("manager_id","select id from user where name like '王%'");
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
==> SELECT id,create_time,name,manager_id,email,age FROM user WHERE (date_format(create_time,’%Y-%m-%d’)=? AND manager_id IN (select id from user where name like ‘王%’))
and嵌套 or嵌套
- or(Consumer consumer)
- and(Consumer consumer)
名字为王姓并且（年龄小于40或邮箱不为空）
name like '王%' and (age<40 or email is not null)
@Test
public void selectByWrapper5(){
QueryWrapper queryWrapper=new QueryWrapper();
queryWrapper.likeRight("name","王").and(wq->wq.lt("age",40).or().isNotNull("email"));
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
=》SELECT id,create_time,name,manager_id,email,age FROM user WHERE (name LIKE ? AND ( (age < ? OR email IS NOT NULL) ))
- .gt() =>大于
名字为王姓或者（年龄小于40并且年龄大于20并且邮箱不为空）
name like '王%' or (age<40 and age>20 and email is not null)
@Test
public void selectByWrapper6(){
QueryWrapper queryWrapper=new QueryWrapper();
queryWrapper.likeRight("name","王")
.or(wq->wq.lt("age",40).gt("age",20).isNotNull("email"));
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
==>SELECT id,create_time,name,manager_id,email,age FROM user WHERE (name LIKE ? OR ( (age < ? AND age > ? AND email IS NOT NULL) ))
nested 正常嵌套
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nested(Consumer consumer)正常嵌套 不带 AND 或者 OR
=> or的优先级小于and的优先级 所以 or要用（条件） 否则先执行and()
（年龄小于40或邮箱不为空）并且名字为王姓
(age<40 or email is not null) and name like '王%'
@Test
public void selectByWrapper7(){
QueryWrapper queryWrapper=new QueryWrapper();
queryWrapper.nested(wp->wp.lt("age",40).or().isNotNull("email"))
.likeRight("name","王");
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
==> SELECT id,create_time,name,manager_id,email,age FROM user WHERE (( (age < ? OR email IS NOT NULL) ) AND name LIKE ?)
last
last()无视优化规则直接拼接到 sql 的最后
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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
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如果确保该字段没有注入风险可以使用
@Test
public void selectByWrapper9(){
QueryWrapper queryWrapper=new QueryWrapper();
queryWrapper.in("age",Arrays.asList(30,31,34,35)).last("limit 1");
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
==> SELECT id,create_time,name,manager_id,email,age FROM user WHERE (age IN (?,?,?,?)) limit 1
查询指定部分列
QueryWrapper条件
继承自 AbstractWrapper ,自身的内部属性 entity 也用于生成 where 条件
及 LambdaQueryWrapper, 可以通过 new QueryWrapper().lambda() 方法获取
方法一:
QueryWrapper queryWrapper=new QueryWrapper();
方法二:
QueryWrapper query= Wrappers.query();
情况一:筛选出指定字段
select id,name from user where name like ‘%雨%’ and age<40
@Test
public void selectByWrapperSupper(){
QueryWrapper queryWrapper=new QueryWrapper();
queryWrapper.select("id","name").like("name","雨").lt("age",40);
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
情况二:排除非指定字段 select id,name,age,email from user where name like ‘%雨%’ and age<40
@Test
public void selectByWrapperSupper2(){
QueryWrapper queryWrapper=new QueryWrapper();
/**
* info.getColumn() 获取列名
*/
queryWrapper.like("name","雨").lt("age",40).select(User.class,info->!info.getColumn().equals("create_time")&&!info.getColumn().equals("manager_id"));
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
condition的作用
- condition的作用是为true时，执行其中的SQL条件，为false时，忽略设置的SQL条件
@Test
public void testCondition(){
String name="王";
String email="";
condition(name,email);
}
private void condition(String name,String email){
QueryWrapper queryWrapper=new QueryWrapper();
/**
* StringUtils.isNotEmpty(name)判断是否为空或者空串
*/
// if(StringUtils.isNotEmpty(name)){
// queryWrapper.like("name",name);
// }
// if(StringUtils.isNotEmpty(email)){
// queryWrapper.like("email",email);
// }
// =>SELECT id,create_time,name,manager_id,email,age FROM user WHERE (name LIKE ?)
queryWrapper.like(StringUtils.isNotEmpty(name),"name",name)
.like(StringUtils.isNotEmpty(email),"email",email);
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
==> SELECT id,create_time,name,manager_id,email,age FROM user WHERE (name LIKE ?)
实体作为条件构造方法的参数
如果想通过对象中某些属性进行模糊查询，我们可以在跟数据库表对应的实体类中相应的属性 标注注解 即可。
- 以实体作为条件构造器 构造方法传入实体 =>会和普通条件构造器同时加载 一般是等值的
@Data
public class User {
//主键
private Long id;
//姓名
@TableField(condition = SqlCondition.LIKE)
private String name;
//年龄
/**
* 小于 @TableField(condition = "%s<#{%s}")
*/
@TableField(condition = "%s<#{%s}")
private Integer age;
//邮箱
private String email;
//直属上级
private Long managerId;
//创建时间
private LocalDateTime createTime;
}
@Test
public void selectByWrapperEntity(){
User whereUser=new User();
whereUser.setName("刘宇浩");
whereUser.setAge(29);
QueryWrapper queryWrapper=new QueryWrapper(whereUser);
queryWrapper.like("name","雨").lt("age",40);
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
queryWrapper .like(“name”,“雨”).lt(“age”,40) ;
=》SELECT id,create_time,name,manager_id,email,age FROM user WHERE name=? AND age=? AND (name LIKE ? AND age < ?)
@Test
public void selectByWrapperEntity(){
User whereUser=new User();
whereUser.setName("刘宇浩");
whereUser.setAge(29);
QueryWrapper queryWrapper=new QueryWrapper(whereUser);
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
@TableField(condition = SqlCondition.LIKE)
private String name;
=》SELECT id,create_time,name,manager_id,email,age FROM user WHERE name LIKE CONCAT(’%’,?,’%’) AND age=?
@Test
public void selectByWrapperEntity(){
User whereUser=new User();
whereUser.setName("刘宇浩");
whereUser.setAge(29);
QueryWrapper queryWrapper=new QueryWrapper(whereUser);
List userList=userMapper.selectList(queryWrapper);
userList.forEach(System.out::println);
}
@TableField(condition = SqlCondition.LIKE)
private String name;
@TableField(condition = “%s<#{%s}”)
private Integer age;
=>SELECT id,create_time,name,manager_id,email,age FROM user WHERE name LIKE CONCAT(’%’,?,’%’) AND age
Lambda条件构造器
MybatisPlus提供了 4种 方式创建lambda条件构造器
1. LambdaQueryWrapper lambdaQueryWrapper=new QueryWrapper().lambda();
2. LambdaQueryWrapper lambdaQueryWrapper2=new LambdaQueryWrapper();
3. LambdaQueryWrapper lambdaQueryWrapper3=Wrappers.lambdaQuery();
4. List userList= new LambdaQueryChainWrapper(userMapper)
.like(User::getName,"雨").ge(User::getAge,20).list();
- QueryWrapper类已经提供了很强大的功能，而lambda条件构造器做的和QueryWrapper的事也是相同的为什么要冗余的存在lambda条件构造器呢？
QueryWrapper是通过自己写表中相应的属性进行构造where条件的，容易发生拼写错误，在编译时不会报错，只有运行时才会报错，而lambda条件构造器是通过调用实体类中的方法，如果方法名称写错，直接进行报错，所以lambda的纠错功能比QueryWrapper要提前很多
@Test
public void selectLambda(){
LambdaQueryWrapper lambdaQueryWrapper3=Wrappers.lambdaQuery();
lambdaQueryWrapper3.like(User::getName,"雨").lt(User::getAge,40);
//where name like '%雨%'
List userList=userMapper.selectList(lambdaQueryWrapper3);
userList.forEach(System.out::println);
}
@Test
public void selectLambda3(){
List userList= new LambdaQueryChainWrapper(userMapper)
.like(User::getName,"雨").ge(User::getAge,20).list();
userList.forEach(System.out::println);
}