java.lang.ClassCastException: java.util.ArrayList cannot be cast to com.github.pagehelper.Page p...

報錯信息：

嚴重: Servlet.service() for servlet [springmvc] in context with path [] threw exception [Request processing failed; nested exception is java.lang.ClassCastException: java.util.ArrayList cannot be cast to com.github.pagehelper.Page] with root cause java.lang.ClassCastException: java.util.ArrayList cannot be cast to com.github.pagehelper.Page at com.*.sellergoods.service.impl.ItemCatServiceImpl.findByParentId(ItemCatServiceImpl.java:124) at com.alibaba.dubbo.common.bytecode.Wrapper7.invokeMethod(Wrapper7.java) at com.alibaba.dubbo.rpc.proxy.javassist.JavassistProxyFactory$1.doInvoke(JavassistProxyFactory.java:47) at com.alibaba.dubbo.rpc.proxy.AbstractProxyInvoker.invoke(AbstractProxyInvoker.java:76) at com.alibaba.dubbo.config.invoker.DelegateProviderMetaDataInvoker.invoke(DelegateProviderMetaDataInvoker.java:52) at com.alibaba.dubbo.rpc.protocol.InvokerWrapper.invoke(InvokerWrapper.java:56) at com.alibaba.dubbo.rpc.filter.ExceptionFilter.invoke(ExceptionFilter.java:62) at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72) at com.alibaba.dubbo.monitor.support.MonitorFilter.invoke(MonitorFilter.java:75) at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72) at com.alibaba.dubbo.rpc.filter.TimeoutFilter.invoke(TimeoutFilter.java:42) at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72) at com.alibaba.dubbo.rpc.protocol.dubbo.filter.TraceFilter.invoke(TraceFilter.java:78) at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72) at com.alibaba.dubbo.rpc.filter.ContextFilter.invoke(ContextFilter.java:73) at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72) at com.alibaba.dubbo.rpc.filter.GenericFilter.invoke(GenericFilter.java:138) at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72) at com.alibaba.dubbo.rpc.filter.ClassLoaderFilter.invoke(ClassLoaderFilter.java:38) at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72) at com.alibaba.dubbo.rpc.filter.EchoFilter.invoke(EchoFilter.java:38) at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:72) at com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply(DubboProtocol.java:104) at com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest(HeaderExchangeHandler.java:96) at com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:173) at com.alibaba.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:51) at com.alibaba.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:57) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748)

代碼：

public PageResult findByParentId(Long parentId,int pageNum,int pageSize) {

 PageHelper.startPage(pageNum, pageSize);
 TbItemCatExample example = new TbItemCatExample();
 Criteria criteria = example.createCriteria();
 criteria.andParentIdEqualTo(parentId);

 List<TbItemCat> all = findAll();
 System.out.println("==將類目數據寫入reid==");
 for (TbItemCat itemCat : all) {
 redisTemplate.boundHashOps("itemCate").put(itemCat.getName(), itemCat.getTypeId());
 }
 System.out.println("==將類目數據寫入reid結束==");
   
 Page<TbItemCat> page= (Page<TbItemCat>)itemCatMapper.selectByExample(example);
   
 return new PageResult(page.getTotal(), page.getResult());
}

　　形成異常緣由是代碼紅色部分,由於pagehelper在設置 PageHelper.startPage(pageNum, pageSize)後到使用 Page<TbItemCat> page= (Page<TbItemCat>)itemCatMapper.selectByExample(example);在這兩段代碼以前都不能都再進行任何查詢否則就會形成類型轉化異常。

　　解決辦法就是將紅色代碼在放在 pagehelper和Page以外：

public PageResult findByParentId(Long parentId,int pageNum,int pageSize) { System.out.println(pageNum); System.out.println(pageSize); System.out.println(parentId); PageHelper.startPage(pageNum, pageSize); TbItemCatExample example = new TbItemCatExample(); Criteria criteria = example.createCriteria(); criteria.andParentIdEqualTo(parentId); Page<TbItemCat> page= (Page<TbItemCat>)itemCatMapper.selectByExample(example); List<TbItemCat> all = findAll(); System.out.println("==將類目數據寫入reid=="); for (TbItemCat itemCat : all) { redisTemplate.boundHashOps("itemCate").put(itemCat.getName(), itemCat.getTypeId()); } System.out.println("==將類目數據寫入reid結束=="); return new PageResult(page.getTotal(), page.getResult()); }

 

原文出處：https://www.cnblogs.com/hwxxbc/p/10993699.html