spring的依赖注入spring的依赖注入有：
1、手工装配（注入值自己编写配置，注解@Autowired @Resource
2、自动装配
关于注解的方式注入
1、首先xml文档里面得加上一个命名空间
xmlns:context=""
"
这个是为了使用
<context:annotation-config />
2、由于@Resource和@Autowired的功能差不多
@Resource默认是按照名称来寻找相应的bean对象，，如果按名称找不到对象就会转而用类型来寻找对象
@Autowired默认是使用类型来寻找对象的
并且@Resource是j2ee的一个包，不是spring里面的，所以解耦比Autowired比较好，所以建议使用@Resource
使用@Resource注入
比如一个类里面有这么两个数据成员：
private PersonDao personDao;private String name = "cutter_point";那么要对personDao如何进行注入呢？
@Resource private PersonDao personDao;//通过注释来进行注入这样，在xml文档里面会按名字来寻找
<?xml version="1.0" encoding="UTF-8"?><beans xmlns=""xmlns:xsi=""xmlns:context=""xsi:schemaLocation=""><context:annotation-config /><bean id="personDao" class="cn.dao.impl.PersonDaoBean"></bean><bean id="personService" class="cn.service.impl.PersonServiceBean"></bean></beans>我们在JUnit里面调用一下函数
package cn.service.impl;import java.util.HashSet;import java.util.Set;import javax.annotation.Resource;import cn.dao.PersonDao;import cn.service.PersonService;public class PersonServiceBean implements PersonService {@Resource private PersonDao personDao;//通过注释来进行注入private String name = "cutter_point";public PersonServiceBean() {// TODO Auto-generated constructor stub}/** * @author xiaofeng * @param 这个是可以生成的构造器 */public PersonServiceBean(PersonDao personDao, String name) {this.personDao = personDao;this.name = name;}public void save(){System.out.println(name);personDao.add();}}调用里面的save方法
package junit.test;import org.junit.BeforeClass;import org.junit.Test;import org.springframework.context.support.AbstractApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import cn.itcast.service.PersonService;public class SpringTest {@BeforeClasspublic static void setUpBeforeClass() throws Exception {}@Test public void instanceSpring(){AbstractApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");PersonService personService = (PersonService)ctx.getBean("personService");personService.save();ctx.close();}}如果注入失败，那么调用personService.save();就会报错，空指针错误，比如我们把xml文档中的
<bean id="personDao" class="cn.itcast.dao.impl.PersonDaoBean"></bean>注释掉，程序报错：
org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘personService’: Injection of resource methods failed; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No unique bean of type [cn.itcast.dao.PersonDao] is defined: Unsatisfied dependency of type [interface cn.itcast.dao.PersonDao]: expected at least 1 matching bean at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:305) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:998) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:472) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380) at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139) at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83) at junit.test.SpringTest.instanceSpring(SpringTest.java:18) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28) at org.junit.runners.ParentRunner.run(ParentRunner.java:236) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No unique bean of type [cn.itcast.dao.PersonDao] is defined: Unsatisfied dependency of type [interface cn.itcast.dao.PersonDao]: expected at least 1 matching bean at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:613) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:431) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:409) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:537) at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:192) at org.springframework.beans.factory.annotation.InjectionMetadata.injectMethods(InjectionMetadata.java:117) at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:302) … 39 more
但是如果去掉注释
注入成功！！
关于set方法注入有时不但是必要的，而且是很有必要的。
