mybatis 自定义实现拦截器插件Interceptor示例

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface Intercepts {
 /**
  * 定义拦截点
  * 只有符合拦截点的条件才会进入到拦截器
  */
 Signature[] value();
}

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({})
public @interface Signature {
 /**
 * 定义拦截的类 Executor、ParameterHandler、StatementHandler、ResultSetHandler当中的一个
 */
 Class<?> type();

 /**
 * 在定义拦截类的基础之上，在定义拦截的方法
 */
 String method();

 /**
 * 在定义拦截方法的基础之上在定义拦截的方法对应的参数，
 * JAVA里面方法可能重载，故注意参数的类型和顺序
 */
 Class<?>[] args();
}

@Intercepts({//注意看这个大花括号，也就这说这里可以定义多个@Signature对多个地方拦截，都用这个拦截器
  @Signature(
    type = ResultSetHandler.class,
    method = "handleResultSets", 
    args = {Statement.class}),
  @Signature(type = Executor.class,
    method = "query",
    args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class})
})

public interface Interceptor {
 Object intercept(Invocation var1) throws Throwable;
 Object plugin(Object var1);
 void setProperties(Properties var1);
}

@Override
 public Object plugin(Object target) {
 //判断是否拦截这个类型对象（根据@Intercepts注解决定），然后决定是返回一个代理对象还是返回原对象。
//故我们在实现plugin方法时，要判断一下目标类型，如果是插件要拦截的对象时才执行Plugin.wrap方法，否则的话，直接返回目标本身。
  if (target instanceof StatementHandler) {
   return Plugin.wrap(target, this);
  }
  return target;
 }

@Intercepts(value = {@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class MyInterceptor implements Interceptor {

 @Override
 public Object intercept(Invocation invocation) throws Throwable {
  StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
  BoundSql boundSql = statementHandler.getBoundSql();
  Object obj = boundSql.getParameterObject();
  String sql = boundSql.getSql();
  if (sql.trim().toUpperCase().startsWith("INSERT")) {
   ReflectUtil.setFieldValue(obj, "rev", 0);
   ReflectUtil.setFieldValue(obj, "createTime", new Date());
   ReflectUtil.setFieldValue(obj, "operateTime", new Date());
   ReflectUtil.setFieldValue(boundSql,"parameterObject", obj);

  } else if (sql.trim().toUpperCase().startsWith("UPDATE")) {
   sql = sql.replaceAll(" set ", " SET ")
     .replaceAll(" Set ", " SET ")
     .replaceAll(" SET ", " SET rev = rev+1, operate_time = NOW(), ");
   ReflectUtil.setFieldValue(boundSql,"sql", sql);
  }
  return invocation.proceed();
 }

 @Override
 public Object plugin(Object o) {
  return Plugin.wrap(o, this);
 }

 @Override
 public void setProperties(Properties properties) {

 }
}

<?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.qxy.mybatis.interceptor.MyInterceptor"/>
 </plugins>

</configuration>

...//省略其他配置
mybatis:
 config-location: classpath:/mybatis-config.xml

...//省略其他配置
mybatis:
 config-location: classpath:/mybatis-config.xml