mybatis自动填充时间字段

对于实体中的 created_on 和 updated_on 来说，它没有必要被开发人员去干预，因为它已经足够说明使用场景了，即在插入数据和更新数据时，记录当前时间，这对于mybatis来说，通过拦截器是可以实现的，记得之前说过在jpa中实现的方法，主要通过jpa的注解实现的，因为今天的mybatis需要用到 java 的拦截器。

定义两个注解

@Retention(RetentionPolicy.RUNTIME)
@Target( {ElementType.FIELD})
public @interface CreatedOnFuncation {

  String value() default "";
}
@Retention(RetentionPolicy.RUNTIME)
@Target( {ElementType.FIELD})
public @interface UpdatedOnFuncation {

  String value() default "";
}

使用这两个注解

@Getter
@Builder(toBuilder = true)
@ToString
public class UserInfo {
  private Long id;
  private String name;
  private String email;

  @CreatedOnFuncation
  private LocalDateTime createdOn;
  @UpdatedOnFuncation
  private LocalDateTime updatedOn;
}

定义拦截器，重写赋值的语句

package com.lind.basic.mybatis;

import com.baomidou.mybatisplus.extension.handlers.AbstractSqlParserHandler;
import java.lang.reflect.Field;
import java.time.LocalDateTime;
import java.util.Properties;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.experimental.Accessors;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlCommandType;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;

/**
 * 时间拦截器.
 */
@EqualsAndHashCode(callSuper = true)
@Data
@Accessors(chain = true)
@Intercepts( {
    @Signature(
        type = org.apache.ibatis.executor.Executor.class,
        method = "update",
        args = {MappedStatement.class, Object.class})})
public class CreateUpdateTimeInterceptor extends AbstractSqlParserHandler implements Interceptor {

  private static final Log logger = LogFactory.getLog(com.baomidou.mybatisplus.extension.plugins.SqlExplainInterceptor.class);

  private Properties properties;

  @Override
  public Object intercept(Invocation invocation) throws Throwable {
    MappedStatement mappedStatement = (MappedStatement) invocation.getArgs()[0];

    // 获取  SQL  命令
    SqlCommandType sqlCommandType = mappedStatement.getSqlCommandType();

    // 获取参数
    Object parameter = invocation.getArgs()[1];

    // 获取私有成员变量
    Field[] declaredFields = parameter.getClass().getDeclaredFields();

    for (Field field : declaredFields) {
      if (field.getAnnotation(CreatedOnFuncation.class) != null) {
        if (SqlCommandType.INSERT.equals(sqlCommandType)) { // insert 语句插入 createTime
          field.setAccessible(true);
          field.set(parameter, LocalDateTime.now());
        }
      }

      if (field.getAnnotation(UpdatedOnFuncation.class) != null) { // insert 或 update 语句插入 updateTime
        if (SqlCommandType.INSERT.equals(sqlCommandType) || SqlCommandType.UPDATE.equals(sqlCommandType)) {
          field.setAccessible(true);
          field.set(parameter, LocalDateTime.now());
        }
      }
    }

    return invocation.proceed();
  }

  @Override
  public Object plugin(Object target) {
    if (target instanceof org.apache.ibatis.executor.Executor) {
      return Plugin.wrap(target, this);
    }
    return target;
  }

  @Override
  public void setProperties(Properties prop) {
    this.properties = prop;
  }
}

添加测试用例

@Test
  public void insert() {
    UserInfo userInfo = UserInfo.builder()
        .name("lind")
        .email("test@sina.com")
        .build();
    userInfoMapper.insert(userInfo);
    System.out.println("userinfo:" + userInfo.toString());
  }

解决是我们所预想的，created_on和updated_on被自动赋上值了。

userinfo:UserInfo
(
id=1085780948955959297, 
name=lind, 
email=test@sina.com, 
createdOn=2019-01-17T14:08:45.665,
updatedOn=2019-01-17T14:08:45.665
)