Mybatis-Plus updateById方法更新无效及空值处理过程

import com.baomidou.mybatisplus.core.conditions.update.UpdateWrapper;

// 假设有一个实体类 User
User user = new User();
user.setId(1); // 需要更新的记录ID
user.setName(null); // 需要更新为空的字段
user.setAge(30);

UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();
updateWrapper.eq("id", user.getId())
             .set("name", user.getName()) // 允许 name 字段更新为 null
             .set("age", user.getAge());

int rows = userMapper.update(null, updateWrapper);
System.out.println("受影响的行数: " + rows);

import com.baomidou.mybatisplus.core.conditions.update.LambdaUpdateWrapper;

User user = new User();
user.setId(1);
user.setName(null); // 需要更新为空的字段
user.setAge(30);

LambdaUpdateWrapper<User> lambdaUpdate = new LambdaUpdateWrapper<>();
lambdaUpdate.eq(User::getId, user.getId())
           .set(User::getName, user.getName()) // 允许 name 字段更新为 null
           .set(User::getAge, user.getAge());

int rows = userMapper.update(null, lambdaUpdate);
System.out.println("受影响的行数: " + rows);

mybatis-plus:
  global-config:
    db-config:
      update-strategy: not_null # 默认值，可以设置为 'ignore' 以允许更新 null

import com.baomidou.mybatisplus.annotation.DbConfig;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MybatisPlusConfig {

    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        // 其他拦截器配置
        return interceptor;
    }

    @Bean
    public DbConfig dbConfig() {
        return new DbConfig();
    }
}

import com.baomidou.mybatisplus.annotation.FieldStrategy;
import com.baomidou.mybatisplus.annotation.TableField;

public class User {
    
    private Long id;
    
    @TableField(updateStrategy = FieldStrategy.IGNORED)
    private String name; // 允许更新为 null
    
    private Integer age;

    // getters and setters
}

import org.springframework.transaction.annotation.Transactional;

@Service
public class UserService {

    @Transactional
    public void updateUser(User user) {
        userMapper.updateById(user);
    }
}