mybatis拦截器与分页插件实例教程

package org.apache.ibatis.plugin;

import java.util.properties;

/**

  * @author clinton begin

  */

public interface interceptor {

  object intercept(invocation invocation) throws throwable;

  object plugin(object target);

  void setproperties(properties properties);

}

<dependency>

  <groupid>org.mybatis.spring.boot</groupid>

  <artifactid>mybatis-spring-boot-starter</artifactid>

  <version> 1.3 . 2 </version>

</dependency>

<dependency>

  <groupid>mysql</groupid>

  <artifactid>mysql-connector-java</artifactid>

  <scope>runtime</scope>

  </dependency>

create table user

(

  id int   auto_increment primary key,

  username varchar( 20 ) null

);

@override

public object intercept(invocation invocation) throws throwable {

logger.info( "进入拦截器" );

object[] args = invocation.getargs();

mappedstatement mappedstatement = (mappedstatement) args[ 0 ];

//获取参数

object param = invocation.getargs()[ 1 ];

boundsql boundsql = mappedstatement.getboundsql(param);

object parameterobject = boundsql.getparameterobject();

/**

  * 判断是否是继承pagevo来判断是否需要进行 分页

  */

if (parameterobject instanceof pagevo) {

  //强转 为了拿到分页数据

  pagevo pagevo = (pagevo) param;

  string sql = boundsql.getsql();

  //获取相关配置

  configuration config = mappedstatement.getconfiguration();

  connection connection = config.getenvironment().getdatasource().getconnection();

  //拼接查询当前条件的sql的总条数

  string countsql = "select count(*) from (" + sql + ") a" ;

  preparedstatement preparedstatement = connection.preparestatement(countsql);

  boundsql countboundsql = new boundsql(config, countsql, boundsql.getparametermappings(), boundsql.getparameterobject());

  parameterhandler parameterhandler = new defaultparameterhandler(mappedstatement, parameterobject, countboundsql);

  parameterhandler.setparameters(preparedstatement);

  //执行获得总条数

  resultset rs = preparedstatement.executequery();

  int count = 0 ;

  if (rs.next()) {

  count = rs.getint( 1 );

  }

  //拼接分页sql

  string pagesql = sql + " limit " + pagevo.getlimit() + " , " + pagevo.getoffset();

  //重新执行新的sql

  donewsql(invocation, pagesql);

  object result = invocation.proceed();

  connection.close();

  //处理新的结构

  pageresult<?> pageresult = new pageresult<list>(pagevo.page, pagevo.rows, count, (list) result);

  list<pageresult> returnresultlist = new arraylist<>();

  returnresultlist.add(pageresult);

  return returnresultlist;

}

return invocation.proceed();

}