条件查询LambdaQueryWrapper
MyBatis-Plus QueryWrapper及LambdaQueryWrapper的使用
假如我们有一张user表，现需要通过user_name查出所有数据
@ApiModel(description = "用户实体")
public class User {
/**
* serialVersionUID
*/
@ApiModelProperty(value = "主键")
private Integer id;
@ApiModelProperty(value = "用户名")
private String username;
@ApiModelProperty(value = "真实昵称")
private String realname;
@ApiModelProperty(value = "性别")
private String sex;
@ApiModelProperty(value = "工号")
private String jobNum;
@ApiModelProperty(value = "状态 0 启用 1 禁用")
private Integer isDel;
@ApiModelProperty(value = "部门")
private Integer departmentId;
private String departmentName;
@ApiModelProperty(value = "密码")
private String password;// 用户密码
@ApiModelProperty(value = "手机")
private String mobile;// 手机
private Integer createUser;
private Integer editUser;
@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
private Date gmtCreate;
@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
private Date gmtUpdate;
}
QueryWrapper
最基础的使用方式是这样
// 查询条件构造器
QueryWrapper<User > wrapper = new QueryWrapper<>();
wrapper.eq("user_name", id);
// 查询操作
List<User > users = userMapper.selectList(wrapper);
然后我们可以引入lambda，避免我们在代码中写类似的于user_name的硬编码
QueryWrapper wrapper = new QueryWrapper<>();
wrapper.lambda().eq(User::getuserName, userName);
List users= userMapper.selectList(wrapper);
LambdaQueryWrapper
为了简化lambda的使用，我们可以改写成LambdaQueryWrapper构造器，语法如下：
LambdaQueryWrapper<User> wrapper = new QueryWrapper<User>().lambda();
wrapper.eq(User::getuserName, userName);
List<User> users= userMapper.selectList(wrapper);
我们可以再次将QueryWrapper.lambda()简化，变成这个样子
LambdaQueryWrapper<User> wrapper = new LambdaQueryWrapper<>();
wrapper.eq(User::getuserName, userName);
List<User> bannerItems = userMapper.selectList(wrapper);
链式查询
MyBatis-Plus还提供了一种链式查询的方式，和上面的代码效果一样。
但是这种写法偏向于炫技，可读性没有上面的代码强，大家可以根据需要自行选择方式。
List<User> bannerItems = new LambdaQueryChainWrapper<>(bannerItemMapper)
.eq(User::getuserName, userName)
.list();
// 增加条件
int count = tcmcConfigTreeService.count(
new LambdaQueryWrapper<TcmcConfigTree>()
.eq(TcmcConfigTree::getNodeName, tcmcConfigTree.getNodeName()).ne(TcmcConfigTree::getId, tcmcConfigTree.getId())
);
LambdaQueryWrapper 条件删除
条件删除符合条件的全部删除
LambdaQueryWrapper<USer> objectLambdaQueryChainWrapper = new LambdaQueryWrapper<>();
objectLambdaQueryChainWrapper.eq(User::getDepartmentId, departmentId);
cEquipmentMapper.delete(objectLambdaQueryChainWrapper);