java - 没有这样的bean异常

Question

无法解决以下异常。尝试使用 spring 依赖注入(inject)的示例。

我收到错误“没有定义名为“book”的 bean，即使我已在 xml 文件中定义了它。

我需要将 xml 中定义的作者和标题打印到控制台。

异常如下:

    Sep 21, 2018 3:05:23 AM org.springframework.context.annotation.AnnotationConfigApplicationContext prepareRefresh
    INFO: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@37bba400: startup date [Fri Sep 21 03:05:23 MDT 2018]; root of context hierarchy
    Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'book' is defined
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:701)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:1180)
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:284)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
        at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1082)
        at com.Rawal.Srishti.SDI.Driver_new.main(Driver_new.java:10)

Book.java:

    package com.Rawal.Srishti.SDI;

    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;

    @Component
    class Book extends Media {
        private static int order = 1;
        private String author;
        @Autowired
        public Book(String title, String author) {
            this.title = title;
            this.author = author;
        }

        public String getAuthor() {
            return author;
        }
        public String getTitle() {
            return title;
        }
        static public int getOrder() {
            return order;
        }
        @Override
        protected String compareString() {
            return getOrder() + getTitle() + getAuthor();
        }
        public String toString() {
            return getTitle() + " by " + getAuthor();
        }

        public int compareTo(Media obj) {
            if(obj instanceof Book) {
                return -(this.getTitle().compareTo(obj.getTitle()));
            } 

            return 444;

        }
    }

驱动程序.java:

package com.Rawal.Srishti.SDI;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Driver_new {
    public static void main(String[] args) {
          @SuppressWarnings("resource")
        ApplicationContext ctx = 
             new AnnotationConfigApplicationContext("Rawal_spring.xml");
          Book m = (Book) ctx.getBean("book", Book.class);
          System.out.println(m.getTitle());
          System.out.println(m.getAuthor());
    }
}

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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

    <bean id = "book" class = "com.Rawal.Srishti.SDI.Book" >
        <constructor-arg index="0" ref="Srishti" />
        <constructor-arg index="1" ref="Rawal"/>
    </bean>

</beans>

Answer 1

您似乎没有使用正确类型的应用程序上下文。

您正在使用的AnnotationConfigApplicationContext是基于注释的，其String参数是要扫描的基本java包，而不是文件名。

您应该使用 ClassPathXmlApplicationContext (如果您的文件位于类路径中)或 FileSystemXmlApplicationContext ，例如:

ApplicationContext ctx = new ClassPathXmlApplicationContext("Rawal_spring.xml");