依赖项注入-maven多模块项目上的java.lang.NoClassDefFoundError

我从事一个maven多模块项目。这些模块是：称为

实体的持久化模块

打包为

jar

，称为

服务的服务模块

打包为

jar

，称为

web

打包为

war

。 pom如下所示：

<groupId>com.af</groupId>
<artifactId>eMuse</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>

<modules>
    <module>entities</module>
    <module>services</module>
    <module>web</module>
</modules>

和web模块配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd">


    <mvc:annotation-driven />

    <context:component-scan base-package="com.af" />
    <import resource="classpath*:services-context.xml"/>
    <!-- Tiles configuration -->

    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.UrlBasedViewResolver">
        <property name="viewClass">
            <value>org.springframework.web.servlet.view.tiles2.TilesView</value>
        </property>
    </bean>
    <bean id="tilesConfigurer"
        class="org.springframework.web.servlet.view.tiles2.TilesConfigurer">
        <property name="definitions">
            <list>
                <value>/WEB-INF/tiles.xml</value>
            </list>
        </property>
    </bean>
    <mvc:default-servlet-handler />
</beans>

我得到一个例外：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'testController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.af.service.StudentService com.af.controller.TestController.studentService; nested exception is java.lang.NoClassDefFoundError: Lcom/af/service/StudentService;

谁能告诉我我做错了什么

---

编辑：我访问服务模块中实体jar的应用程序上下文文件，然后访问web模块中的服务应用程序上下文文件的方式是正确的？

您明确地从web POM中排除了jar：

<exclusions>
            <exclusion>
                <groupId>com.af</groupId>
                <artifactId>entities</artifactId>
            </exclusion>
        </exclusions>

com.af
实体

这是运行时需要的可传递依赖项

您会得到一个NoClassDefFoundError，因为您可以在哪里编译代码，但在运行时需要它

---

只需删除排除项，实体jar将在运行时添加。

但是web模块应该只“知道”和“需要”服务模块。我创建DTO就是为了这个目的。在您的例子中，这是一个需要的DAO，而不是DTO。但在这两种情况下，我相信您的DAO接口在方法的签名中也有DTO类。您可以确保某种松散耦合，但是如果您想要使用一个类，您必须提供它，您可以做的是将dto放在另一个项目中，并且在您的服务层/项目中，您可以将实体类映射到dto类。但我不确定这是否值得付出努力。那进口商品呢：```？Maibe是一个不正确的导入。我删除了排除项。现在我得到了这个错误：

org.springframework.beans.factory.NoSuchBeanDefinitionException:找不到依赖项类型为[com.iquest.af.dao.StudentDAO]的符合条件的bean：至少需要1个符合此依赖项autowire候选项条件的bean。

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd">


    <mvc:annotation-driven />

    <context:component-scan base-package="com.af" />
    <import resource="classpath*:services-context.xml"/>
    <!-- Tiles configuration -->

    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.UrlBasedViewResolver">
        <property name="viewClass">
            <value>org.springframework.web.servlet.view.tiles2.TilesView</value>
        </property>
    </bean>
    <bean id="tilesConfigurer"
        class="org.springframework.web.servlet.view.tiles2.TilesConfigurer">
        <property name="definitions">
            <list>
                <value>/WEB-INF/tiles.xml</value>
            </list>
        </property>
    </bean>
    <mvc:default-servlet-handler />
</beans>

<parent>
    <groupId>com.af</groupId>
    <artifactId>eMuse</artifactId>
    <version>1.0-SNAPSHOT</version>
</parent>
<artifactId>web</artifactId>
<packaging>war</packaging>
<dependencies>
    <dependency>
        <groupId>com.af</groupId>
        <artifactId>services</artifactId>
        <version>1.0-SNAPSHOT</version>
        <exclusions>
            <exclusion>
                <groupId>com.af</groupId>
                <artifactId>entities</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
 <!-- other dependencies-->
 </dependencies>

 @Controller
 public class TestController {

    @Autowired
    private StudentService studentService;

    @RequestMapping(value="/index", method = RequestMethod.GET)
    public String test(Model model){

        StudentModel stud = StudentModelMapper.mapStudentDTO(studentService.getStudentById(1));
        model.addAttribute("name", stud.getFirstName());
        return "index";
    }


 }

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'testController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.af.service.StudentService com.af.controller.TestController.studentService; nested exception is java.lang.NoClassDefFoundError: Lcom/af/service/StudentService;

<exclusions>
            <exclusion>
                <groupId>com.af</groupId>
                <artifactId>entities</artifactId>
            </exclusion>
        </exclusions>