MyBatis自定义拦截器

Mybatis允许你在已经映射语句的执行过程中为某一点进行拦截调用。但是并不是对所有的方法都可以进行这种拦截处理，允许使用插件进行的拦截类如下，具体要拦截该类中哪一个方法则需要关注下mybatis的源码，去指定拦截时的方法入参：支持的拦截类如下：

Executor (update, query, flushStatements, commit, rollback, getTransaction, close, isClosed) ParameterHandler (getParameterObject, setParameters) ResultSetHandler (handleResultSets, handleOutputParameters) StatementHandler (prepare, parameterize, batch, update, query)

自定义拦截器

实现在新增/更新操作时动态为sql注入creationDate以及lastUpdateDate时间字段

定义拦截器时运行时注解

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

    String value() default "";
}

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

    String value() default "";
}

实体类

@Data
@Table(name = "`demo`")
public class Demo implements Serializable {

    /**
     * 主键
     */
    @Id
    @JSONField(serializeUsing = ToStringSerializer.class)
    @GeneratedValue(generator = "JDBC")
    private Long id;

    /**
     * 名称
     */
    private String name;

    /**
     * 创建时间
     */
    @CreateTime
    private Date createdTime;

    private static final long serialVersionUID = 1L;
}

拦截器的核心代码

@Intercepts({@Signature( type= Executor.class, method = "update", args = {MappedStatement.class,Object.class})})
public class CustomInterceptor implements Interceptor {

    @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(CreateTime.class) != null) {
                if (SqlCommandType.INSERT.equals(sqlCommandType)) { // insert 语句插入 createTime
                    field.setAccessible(true);
                    field.set(parameter, new Date());
                }
            }

            if (field.getAnnotation(UpdateTime.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, new Date());
                }
            }
        }

        return invocation.proceed();
    }
}

Mybatis配置文件中添加插件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <plugins>
        <plugin interceptor="com.wueasy.demo.plugin.CustomInterceptor">
        </plugin>
    </plugins>
</configuration>