1.浏览器的错误列表

1. 404

• 访问静态资源文件时:
  • 检查浏览器中请求的路径是否正确
  • 检查文件名是否正确
  • 检查文件位置是否正确
  • 如果以上全部正确仍然404 需要重新编译工程(Build->ReBuild)
• 访问动态资源时:
  • 检查请求的路径是否正确
  • 检查Controller里面RequestMapping注解里面的处理路径是否正确
  • 检查controller包的位置是否在工程自带的包里面
  • 检查@Controller注解是否添加
  • 如果以上全部正确仍然404 需要重新编译工程(Build->ReBuild)

1. 400错误码 : 客户端给服务器传递参数时参数类型转换错误
2. 500错误码: 代表服务器业务代码出错,此时需要看idea里面的报错

2.后端服务器可能报的错误

2.1使用Mybatis可能报的错误

在Spring Boot项目中，当需要使用Mybatis时，需要添加相关的依赖：

<dependency>
    <groupId>mysqlgroupId>
    <artifactId>mysql-connector-javaartifactId>
    <scope>runtimescope>
dependency>
<dependency>
    <groupId>org.mybatis.spring.bootgroupId>
    <artifactId>mybatis-spring-boot-starterartifactId>
    <version>2.2.2version>
dependency>

当添加以上依赖项后，如果启动项目，会提示以下错误：

***************************
APPLICATION FAILED TO START
***************************
 
Description:
 
Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured.
 
Reason: Failed to determine a suitable driver class

因为Spring Boot启动时，如果检测到当前已经添加数据库编程的依赖项，会自动读取连接数据库的配置信息，由于目前尚未配置这些信息，所以，启动会报错！

所以，需要在application.properties中添加配置：

# 连接数据库的参数
spring.datasource.url=jdbc:mysql://localhost:3306/mall_pms?useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai
spring.datasource.username=root
spring.datasource.password=root

由于Spring Boot在启动项目时只会读取以上配置并应用，并不会实际的连接数据库，所以，即使以上配置值是错误的，启动项目时并不会报告错误！

可以在src/test/java的根包下的测试类中进行测试连接：

@SpringBootTest
class CsmallProductApplicationTests {
 
    @Test
    void contextLoads() {
    }
 
    @Autowired
    DataSource dataSource;
 
    @Test
    void testConnection() throws Exception {
        dataSource.getConnection();
    }
 
}

当配置的URL错误（含主机名错误、端口号错误），或MySQL未启动时，将出现以下错误：

com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
 
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

如果数据库名称错误，或无此数据库，将出现以下错误：

java.sql.SQLSyntaxErrorException: Unknown database 'mall_pmsxzxxxxx'

如果用户或密码错误，将出现以下错误：

java.sql.SQLException: Access denied for user 'rootx'@'localhost' (using password: YES)

java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: YES)

java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: NO)

然后，应该及时测试以上功能是否正确，可以在src/test/java下的根包下创建mapper.AlbumMapperTests测试类，

package cn.tedu.csmall.product.mapper;
 
import cn.tedu.csmall.product.pojo.entity.Album;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
 
@SpringBootTest
public class AlbumMapperTests {
 
    @Autowired
    AlbumMapper mapper;
 
    @Test
    void testInsert() {
        Album album = new Album();
        album.setName("某电视的相册");
        album.setDescription("某电视的相册的描述");
        album.setSort(63);
        int rows = mapper.insert(album);
        System.out.println("rows = " + rows);
    }
 
}

在执行测试时，如果此前配置的@MapperScan有误，会出现如下错误：

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'cn.tedu.csmall.product.mapper.AlbumMapperTests': Unsatisfied dependency expressed through field 'mapper'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'cn.tedu.csmall.product.mapper.AlbumMapper' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

如果在XML文件中，的namespace属性值配置有误，或者节点的id属性值配置有误，或者在application.properties中没有正确的配置mybatis.mapper-locations属性，都将出现以下错误：

org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): cn.tedu.csmall.product.mapper.AlbumMapper.insert

如果既没有配置resultType又没有配置resultMap，将会出现以下错误：

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.executor.ExecutorException: A query was run and no Result Maps were found for the Mapped Statement 'c

当在上使用resultType属性，取值却是的id时，将出现以下错误：

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sqlSessionFactory' defined in class path resource [org/mybatis/spring/boot/autoconfigure/MybatisAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.ibatis.session.SqlSessionFactory]: Factory method 'sqlSessionFactory' threw exception; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [C:\Users\pc\IdeaProjects\jsd2204-csmall-product-teacher\target\classes\mapper\BrandMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [C:\Users\pc\IdeaProjects\jsd2204-csmall-product-teacher\target\classes\mapper\BrandMapper.xml]'. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'StandardResultMap'.  Cause: java.lang.ClassNotFoundException: Cannot find class: StandardResultMap

当在

上使用了resultMap，取值错误时（例如取值为类型的全限定名），将出现以下错误：

java.lang.IllegalArgumentException: Result Maps collection does not contain value for cn.tedu.csmall.product.pojo.vo.BrandStandardVO