Understanding Spring-2.3 Annotation assembly from the Beginning-@autowired (4)-required (1)

In this chapter we will discuss in detail the parameter required inside the @autowired.

1.domain (Focus)

Cake Type:

Package Com.raylee.my_new_spring.my_new_spring.ch02.topic_1_9;public class Cake {private String name = "";p ublic string GetName () {return name;} public void SetName (String name) {this.name = name;}}

Chef class:

(1) The following is an error in the Chef class

Package Com.raylee.my_new_spring.my_new_spring.ch02.topic_1_9;import Org.springframework.beans.factory.annotation.autowired;public class Chief {@Autowiredprivate Cake Cake = null;private String name = "";p ublic String getName () {return name;} Public Cake Makeonecake () {if (Cake! = null) {System.out.println (GetName () + "make" + cake.getname ());} else {System.out.println (cake);} return cake;} public void SetName (String name) {this.name = name;}}

Error message:

caused by:org.springframework.beans.factory.NoSuchBeanDefinitionException:No matching bean of type [com.raylee.my_ New_spring.my_new_spring.ch02.topic_1_9.Cake] found for dependency:expected at least 1 bean which qualifies as Autowire C Andidate for this dependency. Dependency annotations: {@org. springframework.beans.factory.annotation.Autowired (Required=true)}
At Org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException ( defaultlistablebeanfactory.java:920)
At Org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency ( defaultlistablebeanfactory.java:789)
At Org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency ( defaultlistablebeanfactory.java:703)
At org.springframework.beans.factory.annotation.autowiredannotationbeanpostprocessor$ Autowiredfieldelement.inject (autowiredannotationbeanpostprocessor.java:474)
... More

(2) The following is an empty object allowed to inject

Package Com.raylee.my_new_spring.my_new_spring.ch02.topic_1_9;import Org.springframework.beans.factory.annotation.autowired;public class Chief {@Autowired (required = false) Private Cake Cake = null;private String name = "";p ublic string GetName () {return name;} Public Cake Makeonecake () {if (Cake! = null) {System.out.println (GetName () + "make" + cake.getname ());} else {System.out.println (cake);} return cake;} public void SetName (String name) {this.name = name;}}

It is important to note that the @Autowired tag is the default force injection of non-empty objects, but we can inject a null object through the Required=false property

2. Test class: (unchanged)

Package Com.raylee.my_new_spring.my_new_spring.ch02.topic_1_9;import Org.junit.test;import Org.junit.runner.runwith;import Org.springframework.beans.factory.annotation.autowired;import Org.springframework.context.applicationcontext;import org.springframework.test.context.ContextConfiguration; Import Org.springframework.test.context.junit4.SpringJUnit4ClassRunner; @RunWith (Springjunit4classrunner.class) @ Contextconfiguration (locations = {"/com/raylee/my_new_spring/my_new_spring/ch02/topic_1_9/ Applicationcontext-test.xml "}) public class Chieftest {@Autowiredprivate ApplicationContext applicationcontext;@ testpublic void Testchief () {Chief Jack = Applicationcontext.getbean (Chief.class); Jack.makeonecake ();}}

3. configuration file (emphasis)

<?xml version= "1.0" encoding= "UTF-8"? ><beans xmlns= "Http://www.springframework.org/schema/beans" xmlns: context= "Http://www.springframework.org/schema/context" xmlns:p= "http://www.springframework.org/schema/p" xmlns: Xsi= "Http://www.w3.org/2001/XMLSchema-instance" xmlns:tx= "Http://www.springframework.org/schema/tx" xmlns:aop= " Http://www.springframework.org/schema/aop "xmlns:util=" Http://www.springframework.org/schema/util "xsi: schemalocation= "Http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/ Spring-beans-3.1.xsd Http://www.springframework.org/schema/util http://www.springframework.org/schema/util/ Spring-util-2.0.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/ Spring-context-3.1.xsdhttp://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/ Spring-tx-3.1.xsdhttp://www.springframework.org/schema/util http://www.springframework.org/schema/util/ Spring-util-3.1.xsdhttP://WWW.SPRINGFRAMEWORK.ORG/SCHEMA/DATA/JPA http://www.springframework.org/schema/data/jpa/ Spring-jpa-1.0.xsdhttp://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/ Spring-beans.xsd HTTP://WWW.SPRINGFRAMEWORK.ORG/SCHEMA/AOP http://www.springframework.org/schema/aop/ Spring-aop.xsd "><bean id=" Jack "class=" Com.raylee.my_new_spring.my_new_spring.ch02.topic_1_9.Chief "p:name= "Jack"/></beans>

To test the example above, we deliberately deleted the cake bean.

Summary: In this chapter we mainly discuss the parameter required inside the @autowired.

Catalog: http://blog.csdn.net/raylee2007/article/details/50611627

My github:https://github.com/raylee2015/my_new_spring.

Understanding Spring-2.3 Annotation assembly from the beginning [email protected](4)-required (1)