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();
 }