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);

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