java.lang.NoClassDefFoundError : com/fasterxml/jackson/core/util/DefaultIndenter

Question

我是 Spring 框架的新手。我正在尝试使用Maven。我只想在项目运行时打开索引页但无法做到

错误说java.lang.NoClassDefFoundError:com/fasterxml/jackson/core/util/DefaultIndenter Error here

父级的pom.xml

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-web-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>4.3.12.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>4.3.12.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.6</version>
        </dependency>

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.9.2</version>
        </dependency>

        <dependency>
            <groupId>com.nishan</groupId>
            <artifactId>LifeStyle</artifactId>
            <version>1.0-SNAPSHOT</version>
        </dependency>
    </dependencies>
</dependencyManagement>

WebModule的

web.xml

    <?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
     version="3.1">

    <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
</web-app>

dispatcher-servlet.xml

    <?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-4.3.xsd
          http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd
          http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
">

    <context:component-scan base-package="com.nishan.webmodule"/>
    <mvc:annotation-driven/>
    <mvc:resources mapping="/static/**" location="/WEB-INF/assets"/>

    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"
    p:prefix="/WEB-INF/views/" p:suffix=".jsp"/>

</beans>

导航到索引页面的 servlet 页面

   @Controller
@RequestMapping(value="/")
public class DefaultServlet {

    @RequestMapping(method=RequestMethod.GET)
    public String index() {
        return "index";
    }
}

Answer 1

根据 <dependencyManagement> 的文档元素(强调我的):

“从该项目继承的项目的默认依赖关系信息。本节中的依赖关系不会立即解析。相反，当从该项目派生的 POM 声明由匹配的 groupId 和artifactId 描述的依赖关系时，如果尚未指定，则本节中的版本和其他值将用于该依赖项。”

换句话说，您可能缺少正确的<dependency>模块 POM 中的定义。