SprintBoot2报错汇总

报错1：SpringBoot找不到bean

Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean

缺少注解 @SpringBootApplication

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报错2：Maven Process terminated

Maven 编译遇到 Process terminated

xml文件标签重复、格式不规范

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报错3：Not registered via @EnableConfigurationProperties

给UserBean添加@ConfigurationProperties时，编译错误，是因为没有被添加为组件。@Component可以解决

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报错4：Junit测试，使用 @SpringBootTest 爆红字，Cannot solve symbol

网上搜了很多方法，主要有

• ①移动test位置到main中
• ②<scope>test</scope> 注释掉
• ③idea配置中删除 SpringBootTest.class 配置项
• 导入的Junit版本冲突，看一下自己的SpringBoot依赖版本

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错误5：浏览器访问 “Whitelabel Error Page“

看看是不是Application 启动类 的位置不对，启动类与扫描包同级

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报错6：运行时异常 UnsupportedClassVersionError

java: java.lang.UnsupportedClassVersionError: org/springframework/boot/configurationprocessor/ConfigurationMetadataAnnotationProcessor has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 52.0

原因：

高版本的编译后文件，无法在低版本环境运行

那问题来了，哪来的高版本编译后文件？ConfigurationMetadataAnnotationProcessor 显然是 spring-boot-starter-parent 依赖引入的，3.02 换低版本 2.3.4即可

误删pom.xml，bug居然没了，大无语.....

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错误7： Error resolving template [index]

[THYMELEAF][http-nio-8080-exec-5]

Exception processing template "index": Error resolving template [index], template might not exist or might not be accessible by any of the configured Template Resolvers

org.thymeleaf.exceptions.TemplateInputException: Error resolving template [index], template might not exist or might not be accessible by any of the configured Template Resolvers

原因：

Thymeleaf的声明放错了地方。。。，Thymeleaf 语法没报错，但页面解析不出来。

只要有一个页面使用了Thymeleaf，每个Html都要加Thymeleaf表头

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8 java.io.IOException: Could not find resource mybatis-config.xml

mybatis总配置文件放错位置了，应该在resources下

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9 org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.atguigu.mapper.UserMapper.selectUser

总配置文件映射错位

<mappers>
    <mapper resource="com.atguigu.mapper.UserMapper"/>
</mappers>

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10 Error building SqlSession

### Error building SqlSession.
### The error may exist in com/atguigu/mapper/UserMapper.xml
### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.io.IOException: Could not find resource com/atguigu/mapper/UserMapper.xml

解决1：mybatis-config.xml 的 mapper resource 路径写错了，应该以 / 作为分割

把conf.xml文件下的<mapper>里的 resource="com.easy.mapping.userMapper.xml" 改为 resource="com/easy/mapping/userMapper.xml"

解决2：静态资源拦截，在pom添加

    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>

　　网上其他的解决方案：

class 路径下，接口和它的Mapper配置文件必须同名

接口和它的Mapper配置文件必须同一个包下

官方给出全限定名保证不出错

你可以多找找与路径相关的

在查询上面resultType="com.bing.pojo.User"这个有时候也需要全限定名

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11 sql异常：You can't specify target table 'grade_tbl' for update in FROM clause

需求：删除重复条目（删除自动编号不同，其他信息相同的条目）

解决方法，给临时表起别名

# 错误
delete from grade_tbl where 自动编号 not in (select min(自动编号) from grade_tbl group by 学号,姓名,课程编号,课程名称,分数);
# 正确
delete from grade_tbl
       where 自动编号
       not in (select * from (select min(自动编号) from grade_tbl group by 学号, 姓名, 课程编号, 课程名称, 分数) as temp);

　　

12 java.lang.NullPointerException 空指针异常

错误：在实现层，测试BookService，增删改查都是空指针异常。

解决：容器中没有BookService组件，BookService 字段上添加@Autowired

13、@Autowired的Service层报错

没有加入容器，service添加@service