MyBatis framework interceptors simple to use

Interceptor

       Is a plugin (plugin extensions) MyBatis provides. Representative interceptor may intercept code database access operations, i.e., operations Statement
intercepting, can modify the SQL statement is executed, access to the database may additionally be implemented a number of data processing and calculation.
Not many usage scenarios, for blocking tools to achieve some type of SQL. Granularity is too rough, affect the efficiency.

Specific code

Custom interceptors (Interceptor interfaces required to implement, with the notes to achieve)

//声明拦截器
@Intercepts(value = {
	  /**
	   * 要拦截的具体类型
	   * method：query对应statement中的executeQuery()，update 对应statement中的executeUpdate()
	   * type：拦截的驱动的类型，Executor是MyBatis提供的底层访问数据库时的封装接口，类似于JDBC的Statement
	   * args：通知MyBatis框架，当前拦截器中拦截方法intercept参数invocation需要提供多少个参数
	   */
	  @Signature(method = "query", type=Executor.class,args= {MappedStatement.class,Object.class,RowBounds.class,ResultHandler.class})
 	}
)
public class PageInterceptor implements Interceptor{
	 @Override
	 public Object intercept(Invocation arg0) throws Throwable {
	 //获取需要的参数信息,提取顺序和注解声明顺序相关
	 Object[] param = arg0.getArgs();
	 //获取第一个参数MappedStatement
	 MappedStatement mStatement = (MappedStatement) param[0];
	 //获取参数表
	 Object paramter = param[1];
	 //获取查询结果处理器，类似于ResultSet
	 ResultHandler handler = (ResultHandler)param[3];
	 //获取具体被拦截的方法
	 Method method = arg0.getMethod();
	 //获取执行器，类似Statement
	 Executor target = (Executor) arg0.getTarget();
	 //通过MappedStatement获取的sql语句（不论是定义的注解或文件）
	 BoundSql bSql = mStatement.getBoundSql(paramter);
	  
	 //将获取到的sql语句进行预处理
	 String pageSql = this.HandleSqlColumn(bSql.getSql(), paramter);
	 //定义一个新的sql，替换在配置文件或注解中的sql
	 BoundSql pageBoundSql = new BoundSql(mStatement.getConfiguration(), pageSql, bSql.getParameterMappings(), paramter);
	 //定义一个缓存，当执行查询后，会将查询结果存储到一级缓存中
	 CacheKey cacheKey = target.createCacheKey(mStatement, paramter, RowBounds.DEFAULT, pageBoundSql);
	 //执行
	 List<Object> temp = target.query(mStatement, paramter, RowBounds.DEFAULT, handler, cacheKey, pageBoundSql);
	 System.out.println("执行拦截器");
	  return temp;
	 }
	 
	 private String HandleSqlColumn(String sql, Object parame) { 
  		return sql;
 	}
}

Configuration file

<!-- 配置拦截器插件 -->
 <plugins>
  	<plugin interceptor="com.mfqh.interceptor.PageInterceptor"></plugin>
 </plugins>

Detect

It can be found: two interceptions carried out in the course of the entire query to be processed