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逻辑删除

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插件

逻辑删除作为一个常见需求，MyBatisPlus为我们提供了简便的方法实现逻辑删除功能（通过MyBatisPlus的逻辑删除插件实现）。

**注意：逻辑删除插件只对自动注入的sql起效**

步骤如下：

- 配置逻辑删除插件
- 在实体类字段上加入`@TableLogic`注解

## 准备数据表

```sql
CREATE TABLE `t_country` (
`country_id`  int(10) NOT NULL AUTO_INCREMENT,
`country_name`  varchar(16) NOT NULL DEFAULT '' ,
`is_delete`  tinyint(1) NOT NULL DEFAULT 0 ,
PRIMARY KEY (`coutry_id`)
)
;

INSERT INTO `t_country`(country_name) VALUES
 ("中国"),("美国"),('英国'),('澳大利亚');
```

## 定义Mapper以及实体类

CountryMapper定义如下：

```java
public interface CountryMapper extends BaseMapper<Country> {

}
```

实体类定义如下：

```java
public class Country {

@TableId
    private Integer countryId;
    private String countryName;
    
    @TableLogic
    private Integer isDelete;

public Country() {
    }

public Country(Integer countryId, String countryName) {
        this.countryId = countryId;
        this.countryName = countryName;
    }

public Integer getCountryId() {
        return countryId;
    }

public void setCountryId(Integer countryId) {
        this.countryId = countryId;
    }

public String getCountryName() {
        return countryName;
    }

public void setCountryName(String countryName) {
        this.countryName = countryName;
    }

@Override
    public String toString() {
        return "Country{" +
                "countryId=" + countryId +
                ", countryName='" + countryName + '\'' +
                '}';
    }
}
```

## 配置逻辑删除插件

![](https://www.1024phper.com/wp-content/uploads/2021/04/QQ截图20210425124719.jpg)

## 测试逻辑删除功能

```java
int america = 2;
mapper.deleteById(america);
// UPDATE t_country SET is_delete=1 WHERE country_id=?
mapper.selectById(america);
// SELECT country_id AS countryId,country_name AS countryName,is_delete AS isDelete 
// FROM t_country WHERE country_id=? AND is_delete=0
```

## SpringBoot中使用逻辑删除

- 添加逻辑删除字段

```sql
ALTER TABLE `t_employee`
ADD COLUMN `is_delete`  tinyint(1) NOT NULL DEFAULT 0 AFTER `update_time`;
```

* 配置

```
mybatis-plus:
  configuration:
    map-underscore-to-camel-case: true
  mapper-locations: classpath:mapper/*Mapper.xml
  global-config:
    db-config:
      table-prefix: t_
      id-type: auto
      logic-delete-field: is_delete # 逻辑删除字段
      logic-delete-value: 1 # 删除时字段值
      logic-not-delete-value: 0 # 未删除时字段值
```

* 在实体类中添加isDelete字段，并添加@TableLogic注解。

- 测试

```java
@Test
void test6 ()
{
    int i = employeeMapper.deleteById(9);
    // UPDATE t_employee SET is_delete=1 WHERE emp_id=? AND is_delete=0 
    
    employeeMapper.selectById(9);
    // SELECT emp_id,age,emp_name,email,sex,add_time,update_time,is_delete FROM t_employee WHERE emp_id=? AND is_delete=0
}
```

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