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
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| @ApiModel(description = "用户实体") public class User {
@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;
@ApiModelProperty(value = "手机") private String mobile;
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; }
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QueryWrapper
最基础的使用方式是这样
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| QueryWrapper<User > wrapper = new QueryWrapper<>(); wrapper.eq("user_name", id);
List<User > users = userMapper.selectList(wrapper);
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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
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| QueryWrapper wrapper = new QueryWrapper<>(); wrapper.lambda().eq(User::getuserName, userName); List users= userMapper.selectList(wrapper);
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LambdaQueryWrapper
为了简化lambda的使用,我们可以改写成LambdaQueryWrapper构造器,语法如下:
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| LambdaQueryWrapper<User> wrapper = new LambdaQueryWrapper<>(); wrapper.eq(User::getuserName, userName); List<User> bannerItems = userMapper.selectList(wrapper);
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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。
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| List<User> bannerItems = new LambdaQueryChainWrapper<>(bannerItemMapper) .eq(User::getuserName, userName) .list();
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LambdaQueryWrapper 条件删除
条件删除符合条件的全部删除 LambdaQueryWrapper
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| objectLambdaQueryChainWrapper = new LambdaQueryWrapper<>(); objectLambdaQueryChainWrapper.eq(User::getDepartmentId, departmentId); cEquipmentMapper.delete(objectLambdaQueryChainWrapper);
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