条件构造器AbstractWrapper（公共父类）
allEq：all等于
allEq(Map<R, V> params)
allEq(Map<R, V> params, boolean null2IsNull)
allEq(boolean condition, Map<R, V> params, boolean null2IsNull)
//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'
//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
eq：等于
eq(R column, Object val)
eq(boolean condition, R column, Object val)
//eq("name", "老王")--->name = '老王'
ne ：不等于<>
ne(R column, Object val)
ne(boolean condition, R column, Object val)
//ne("name", "老王")--->name <> '老王'
ge：大于等于>=
ge(R column, Object val)
ge(boolean condition, R column, Object val)
//ge("age", 18)--->age >= 18
It：小于<
lt(R column, Object val)
lt(boolean condition, R column, Object val)
//lt("age", 18)--->age < 18
Ie：小于等于<=
le(R column, Object val)
le(boolean condition, R column, Object val)
//le("age", 18)--->age <= 18
between：值1 <=xx<= 值2
between(R column, Object val1, Object val2)
between(boolean condition, R column, Object val1, Object val2)
//between("age", 18, 30)--->age between 18 and 30
notBetween：NOT BETWEEN 值1 AND 值2
notBetween(R column, Object val1, Object val2)
notBetween(boolean condition, R column, Object val1, Object val2)
//notBetween("age", 18, 30)--->age not between 18 and 30
like：LIKE '%值%'
like(R column, Object val)
like(boolean condition, R column, Object val)
//like("name", "王")--->name like '%王%'
notLike：NOT LIKE '%值%'
notLike(R column, Object val)
notLike(boolean condition, R column, Object val)
//notLike("name", "王")--->name not like '%王%'
likeLeft：LIKE '%值'
likeLeft(R column, Object val)
likeLeft(boolean condition, R column, Object val)
//likeLeft("name", "王")--->name like '%王'
likeRight：LIKE '值%'
likeRight(R column, Object val)
likeRight(boolean condition, R column, Object val)
//likeRight("name", "王")--->name like '王%'
isNull
isNull(R column)
isNull(boolean condition, R column)
//isNull("name")--->name is null
isNotNull
isNotNull(R column)
isNotNull(boolean condition, R column)
//isNotNull("name")--->name is not null
in：字段 IN (value.get(0), value.get(1), ...)
in(R column, Collection<?> value)
in(boolean condition, R column, Collection<?> value)
//用法1：in("age",{1,2,3})--->age in (1,2,3)
//用法2：in("age", 1, 2, 3)--->age in (1,2,3)推荐
notIn：字段 NOT IN (value.get(0), value.get(1), ...)
notIn(R column, Collection<?> value)
notIn(boolean condition, R column, Collection<?> value)
//用法1：notIn("age",{1,2,3})--->age not in (1,2,3)
//用法2：notIn("age", 1, 2, 3)--->age not in (1,2,3)
inSql：字段 IN ( sql语句 )
inSql(R column, String inValue)
inSql(boolean condition, R column, String inValue)
//用法1：inSql("age", "1,2,3,4,5,6")--->age in (1,2,3,4,5,6)
//用法2：inSql("id", "select id from table where id < 3")--->id in (select id from table where id < 3)
notInSql：字段 NOT IN ( sql语句 )
notInSql(R column, String inValue)
notInSql(boolean condition, R column, String inValue)
//用法1：notInSql("age", "1,2,3,4,5,6")--->age not in (1,2,3,4,5,6)
//用法2：notInSql("id", "select id from table where id < 3")--->id not in (select id from table where id < 3)
or：拼接 OR
or()
or(boolean condition)
//queryWrapper.eq("id",2);
//queryWrapper.or();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，默认使用and连接)
//queryWrapper.eq("name","小红");
//where id = 2 or name = '小红' :写了or
//where id = 2 and name = '小红' :没写or默认为and
plus，分页
//Spring boot方式
@EnableTransactionManagement
@Configuration
@MapperScan("com.baomidou.cloud.service.*.mapper*")//这里扫描了之后，就不用再在启动类上面重复扫描了
public class MybatisPlusConfig {
@Bean
public PaginationInterceptor paginationInterceptor() {
PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
// 设置请求的页面大于最大页后操作， true调回到首页，false 继续请求 默认false
// paginationInterceptor.setOverflow(false);
// 设置最大单页限制数量，默认 500 条，-1 不受限制
// paginationInterceptor.setLimit(500);
// 开启 count 的 join 优化,只针对部分 left join
paginationInterceptor.setCountSqlParser(new JsqlParserCountOptimize(true));
return paginationInterceptor;
}
}
-
在dao层需要加上分页方法
public interface UserMapper {//可以继承或者不继承BaseMapper
/**
* <p>
* 查询 : 根据state状态查询用户列表，分页显示
* </p>
*
* @param page 分页对象,xml中可以从里面进行取值,传递参数 Page 即自动分页,必须放在第一位(你可以继承Page实现自己的分页对象)
* @param state 状态
* @return 分页对象
*/
IPage<User> selectPageVo(Page<?> page, Integer state);
}
-
UserServiceImpl.java 调用分页方法
public IPage<User> selectUserPage(Page<User> page, Integer state) {
// 不进行 count sql 优化，解决 MP 无法自动优化 SQL 问题，这时候你需要自己查询 count 部分
// page.setOptimizeCountSql(false);
// 当 total 为小于 0 或者设置 setSearchCount(false) 分页插件不会进行 count 查询
// 要点!! 分页返回的对象与传入的对象是同一个
return userMapper.selectPageVo(page, state);
}
简单的介绍一下什么是Page
//源码
public class Page<T> implements IPage<T> {
private static final long serialVersionUID = 8545996863226528798L;
//查询数据列表
protected List<T> records = Collections.emptyList();
//总数
protected long total = 0;
//每页显示条数，默认 10
protected long size = 10;
//当前页
protected long current = 1;
//排序字段信息
@Getter
@Setter
protected List<OrderItem> orders = new ArrayList<>();
//自动优化 COUNT SQL
protected boolean optimizeCountSql = true;
//是否进行 count 查询
protected boolean isSearchCount = true;
//是否命中count缓存
protected boolean hitCount = false;
//countId
@Getter
@Setter
protected String countId;
// countId
@Getter
@Setter
protected Long maxLimit;
/**
*说明具体的意思
*records 用来存放查询出来的数据
*total 返回记录的总数
*size 每页显示条数，默认 10
*current 当前页,默认1
*orders 排序字段信息
*optimizeCountSql 自动优化 COUNT SQL,默认true
*isSearchCount 是否进行 count 查询,默认true
*hitCount 是否命中count缓存,默认false
*/
//构建一个Page
Page<T> page = new Page<T>(pageNum,pageSize)
