Wrapper条件构造器

Wrapper：条件构造抽象类，超类；

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；

常用的案例：

先看版本在看例子：

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.4.1</version>
</dependency>

@Override
public void insert() {
    SystemUser systemUser = new SystemUser();
    systemUser.setUsername("shun");
    super.getBaseMapper().insert(systemUser);
}

@Override
public void delete() {
    // 根据ID删除
    super.getBaseMapper().deleteById(1);
    // Wrapper条件删除
    QueryWrapper<SystemUser> updateWrapper = new QueryWrapper<>();
    updateWrapper.eq("id", 2);
    super.getBaseMapper().delete(updateWrapper);
    // 批量删除
    List<Integer> idList = new ArrayList<>();
    idList.add(1);
    idList.add(2);
    super.getBaseMapper().deleteBatchIds(idList);
}

@Override
public void modify() {
    SystemUser systemUser = new SystemUser();
    systemUser.setId(1);
    systemUser.setUsername("username");
    //
    super.getBaseMapper().updateById(systemUser);
    //修改值
    systemUser = new SystemUser();
    systemUser.setUsername("shun");
    //修改条件
    UpdateWrapper<SystemUser> updateWrapper = new UpdateWrapper<>();
    updateWrapper.eq("id", 2);
    int updateOpt = super.getBaseMapper().update(systemUser, updateWrapper);
    System.out.println(updateOpt);


}

@Override
public void selectOne() {
    QueryWrapper<SystemUser> queryWrapper = new QueryWrapper<SystemUser>();
    queryWrapper.eq("username", "shun");
    SystemUser systemUser = super.getBaseMapper().selectOne(queryWrapper);
    System.out.println(systemUser);
}

@Override
public void selectCount() {
    QueryWrapper<SystemUser> queryWrapper = new QueryWrapper<SystemUser>();
    queryWrapper.eq("username", "shun");
    Integer count = super.getBaseMapper().selectCount(queryWrapper);
    System.out.println(count);
}

@Override
public void selectList() {
    // 为null查询全部
    List<SystemUser> list = super.getBaseMapper().selectList(null);
    System.out.println(list);
}

@Override
public void selectMaps() {
    QueryWrapper<SystemUser> queryWrapper = new QueryWrapper<SystemUser>();
    queryWrapper.eq("username", "shun");
    List<Map<String, Object>> maps = super.getBaseMapper().selectMaps(queryWrapper);
    for (Map<String, Object> map : maps) {
        System.out.println(map);
    }
}

@Override
public void selectPage() {
    Page<SystemUser> page = new Page<>(1, 10);
    QueryWrapper<SystemUser> queryWrapper = new QueryWrapper<>();
    IPage<SystemUser> userIPage = super.getBaseMapper().selectPage(page, queryWrapper);
    System.out.println(userIPage);
}

@Override
public void selectMapsPage() {
    Page<Map<String, Object>> page = new Page<>(1, 10);
    QueryWrapper<SystemUser> queryWrapper = new QueryWrapper<>();
    IPage<Map<String, Object>> mapIPage = super.getBaseMapper().selectMapsPage(page, queryWrapper);
    System.out.println(mapIPage);
}

其它实例