javaweb报错问题以及解决方案

问题（报错信息）：Application Server was not connected before run configuration stop, reason: javax.management.InstanceNotFoundException: Catalina:type=Server

解决方案：在使用idea启动tomcat的时候控制台报这个错误，原因是本机的8080端口被占用，在idea里把tomcat的启动端口从新换一个即可

问题（报错信息）：org.apache.taglibs.standard.tlv.JstlCoreTLV

根本原因：缺少一个standard-1.1.2.jar

解决办法：在pom.xml中添加standard依赖

<dependency> <groupId>taglibs</groupId> <artifactId>standard</artifactId> <version>1.0.6</version> </dependency>

问题（报错信息）：javax.el.PropertyNotFoundException: The class ‘java.lang.String’ does not have the property ‘id’.

原因：el表达式书写不正确

错误的jsp页面

<c:forEach items="list" var="carlist"> <tr> <td>${carlist.id}</td> <td>${carlist.brand}</td> <td>${carlist.type}</td> <td>￥${carlist.price}</td> <td> <a href="delete?id=${carlist.id}" class="layui-btn layui-btn-normal">删除</a> <a href="alter?id=${carlist.id}" class="layui-btn layui-btn-normal">修改</a> </td> </tr> </c:forEach>

正确的jsp页面

<c:forEach items="${list}" var="carlist"> <tr> <td>${carlist.id}</td> <td>${carlist.brand}</td> <td>${carlist.type}</td> <td>￥${carlist.price}</td> <td> <a href="delete?id=${carlist.id}" class="layui-btn layui-btn-normal">删除</a> <a href="alter?id=${carlist.id}" class="layui-btn layui-btn-normal">修改</a> </td> </tr> </c:forEach>

正确的el表达式应该是这样：${变量}

报错Unable to find a @SpringBootConfiguration, you need to use @ContextConfiguration or @SpringBootTest(classes=…) with your test

在spring-boot项目的ApplicationTests类中测试报这个错误 是因为@SpringBootTest注解没有指定classess属性的值 classess的值就是spring-boot项目的启动类

@SpringBootTest(classes = SsmcarApplication.class) class SsmcarApplicationTests {

如果不指定还会报空指针异常 junit依赖建议使用与spring-boot结合的依赖

<dependency> <groupId>org.junit.vintage</groupId> <artifactId>junit-vintage-engine</artifactId> </dependency>

报错：com.mysql.cj.exceptions.CJException: Access denied for user ‘root’@‘localhost’ (using password: YES)

springboot项目在配置数据源的时候应该在密码栏加上双引号，特别是以0开头的密码

datasource: driver-class-name: com.mysql.cj.jdbc.Driver type: com.alibaba.druid.pool.DruidDataSource url: jdbc:mysql://localhost:3306/ssm?serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true username: root password: "password"