springboot3整合mybatis-plus常见的两个错误xxx.NullBean和factoryBeanObjectType: java.lang.String

文章讲述了在将SpringBoot版本从3.1.7升级到3.2.1时遇到的两个问题：BeanNotOfRequiredTypeException关于DdlApplicationRunner类型错误和IllegalArgumentException在factoryBeanObjectType属性上的问题。作者提供了相应的解决方法，包括添加DdlApplicationRunnerbean并调整mybatis-plus-boot-starter的版本和排除依赖。

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1:第一个错

pom

 <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.1.7</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.zd</groupId>
    <artifactId>Mybatis-Plus-Helloworld</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Mybatis-Plus-Helloworld</name>
    <description>Mybatis-Plus-Helloworld</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.3</version>
        </dependency>

    </dependencies>

报错

org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'ddlApplicationRunner' is expected to be of type 'org.springframework.boot.Runner' but was actually of type 'org.springframework.beans.factory.support.NullBean'

解决办法

增加 DdlApplicationRunner bean

    @Bean
    public DdlApplicationRunner ddlApplicationRunner(@Autowired(required = false) List ddlList) {
        return new DdlApplicationRunner(ddlList);
    }

适配 mybatis-plus-boot-starter 最低版本为 3.5.3

2.第二个错

将springboot版本换成3.2.1，其余不变

pom

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.2.1</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

报错

java.lang.IllegalArgumentException: Invalid value type for attribute 'factoryBeanObjectType': java.lang.String

解决办法

修改pom

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.zd</groupId>
    <artifactId>Mybatis-Plus-Helloworld</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Mybatis-Plus-Helloworld</name>
    <description>Mybatis-Plus-Helloworld</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.3</version>
            <exclusions>
                <exclusion>
                    <groupId>org.mybatis</groupId>
                    <artifactId>mybatis-spring</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>3.0.3</version>
        </dependency>
    </dependencies>