Spring常用注解汇总.docx
- 文档编号:4516048
- 上传时间:2022-12-01
- 格式:DOCX
- 页数:20
- 大小:24.09KB
Spring常用注解汇总.docx
《Spring常用注解汇总.docx》由会员分享,可在线阅读,更多相关《Spring常用注解汇总.docx(20页珍藏版)》请在冰豆网上搜索。
Spring常用注解汇总
传统的Spring做法是使用.xml文件来对bean进行注入或者是配置aop、事物,这么做有两个缺点:
1、如果所有的内容都配置在.xml文件中,那么.xml文件将会十分庞大;如果按需求分开.xml文件,那么.xml文件又会非常多。
总之这将导致配置文件的可读性与可维护性变得很低。
2、在开发中在.java文件和.xml文件之间不断切换,是一件麻烦的事,同时这种思维上的不连贯也会降低开发的效率。
为了解决这两个问题,Spring引入了注解,通过"@XXX"的方式,让注解与JavaBean紧密结合,既大大减少了配置文件的体积,又增加了JavaBean的可读性与内聚性。
不使用注解:
先看一个不使用注解的Spring示例,在这个示例的基础上,改成注解版本的,这样也能看出使用与不使用注解之间的区别,先定义一个老虎:
packagecom.spring.model;
publicclassTiger{
privateStringtigerName="TigerKing";
publicStringtoString(){
return"TigerName:
"+tigerName;
}
}
再定义一个猴子:
packagecom.spring.model;
publicclassMonkey{
privateStringmonkeyName="MonkeyKing";
publicStringtoString(){
return"MonkeyName:
"+monkeyName;
}
}
定义一个动物园:
packagecom.spring.model;
publicclassZoo{
privateTigertiger;
privateMonkeymonkey;
publicTigergetTiger(){
returntiger;
}
publicvoidsetTiger(Tigertiger){
this.tiger=tiger;
}
publicMonkeygetMonkey(){
returnmonkey;
}
publicvoidsetMonkey(Monkeymonkey){
this.monkey=monkey;
}
publicStringtoString(){
returntiger+"\n"+monkey;
}
}
spring的配置文件这么写:
xmlversion="1.0"encoding="UTF-8"?
> xmlns="http: //www.springframework.org/schema/beans" xmlns: xsi="http: //www.w3.org/2001/XMLSchema-instance" xmlns: p="http: //www.springframework.org/schema/p" xmlns: context="http: //www.springframework.org/schema/context" xsi: schemaLocation="http: //www.springframework.org/schema/beans http: //www.springframework.org/schema/beans/spring-beans-3.0.xsd http: //www.springframework.org/schema/context http: //www.springframework.org/schema/context/spring-context-3.0.xsd ">
测试方法:
publicclassTestAnnotation{
/**
*不使用注解
*/
@Test
publicvoidtest(){
//读取配置文件
ApplicationContextctx=newClassPathXmlApplicationContext("applicationContext2.xml");
Zoozoo=(Zoo)ctx.getBean("zoo");
System.out.println(zoo.toString());
}
}
都很熟悉,权当复习一遍了。
1、@Autowired
@Autowired顾名思义,就是自动装配,其作用是为了消除代码Java代码里面的getter/setter与bean属性中的property。
当然,getter看个人需求,如果私有属性需要对外提供的话,应当予以保留。
@Autowired默认按类型匹配的方式,在容器查找匹配的Bean,当有且仅有一个匹配的Bean时,Spring将其注入@Autowired标注的变量中。
因此,引入@Autowired注解,先看一下spring配置文件怎么写:
xmlversion="1.0"encoding="UTF-8"?
>
//www.springframework.org/schema/beans"xmlns: xsi="http: //www.w3.org/2001/XMLSchema-instance"xmlns: p="http: //www.springframework.org/schema/p"xmlns: context="http: //www.springframework.org/schema/context"xsi: schemaLocation="http: //www.springframework.org/schema/beanshttp: //www.springframework.org/schema/beans/spring-beans-3.0.xsdhttp: //www.springframework.org/schema/contexthttp: //www.springframework.org/schema/context/spring-context-3.0.xsd"> component-scanbase-package="com.spring"/> 注意第13行,使用必须告诉spring一下我要使用注解了,告诉的方式有很多, component-scanbase-package="xxx"/>是一种最简单的,spring会自动扫描xxx路径下的注解。 看到第15行,原来zoo里面应当注入两个属性tiger、monkey,现在不需要注入了。 再看下,Zoo.java也很方便,把getter/setter都可以去掉: packagecom.spring.model; importorg.springframework.beans.factory.annotation.Autowired; publicclassZoo{ @Autowired privateTigertiger; @Autowired privateMonkeymonkey; publicStringtoString(){ returntiger+"\n"+monkey; } } 这里@Autowired注解的意思就是,当Spring发现@Autowired注解时,将自动在代码上下文中找到和其匹配(默认是类型匹配)的Bean,并自动注入到相应的地方去。 有一个细节性的问题是,假如bean里面有两个property,Zoo.java里面又去掉了属性的getter/setter并使用@Autowired注解标注这两个属性那会怎么样? 答案是Spring会按照xml优先的原则去Zoo.java中寻找这两个属性的getter/setter,导致的结果就是初始化bean报错。 OK,假设此时我把.xml文件的16行、17行两行给去掉,再运行,会抛出异常: org.springframework.beans.factory.BeanCreationException: Errorcreatingbeanwithname'zoo': Injectionofautowireddependenciesfailed;nestedexceptionisorg.springframework.beans.factory.BeanCreationException: Couldnotautowirefield: privatecom.spring.model.Tigercom.spring.model.Zoo.tiger;nestedexceptionisorg.springframework.beans.factory.NoSuchBeanDefinitionException: Nomatchingbeanoftype[com.spring.model.Tiger]foundfordependency: expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java: 285) atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java: 1074) atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java: 517) atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java: 456) atorg.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java: 291) atorg.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java: 222) atorg.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java: 288) atorg.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java: 190) atorg.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java: 580) atorg.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java: 895) atorg.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java: 425) atorg.springframework.context.support.ClassPathXmlApplicationContext. 139) atorg.springframework.context.support.ClassPathXmlApplicationContext. 83) atcom.spring.test.TestAnnotation.test(TestAnnotation.java: 16) atsun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethod) atsun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java: 39) atsun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java: 25) atjava.lang.reflect.Method.invoke(Method.java: 597) atorg.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java: 45) atorg.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java: 15) atorg.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java: 42) atorg.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java: 20) atorg.junit.runners.ParentRunner.runLeaf(ParentRunner.java: 263) atorg.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java: 68) atorg.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java: 47) atorg.junit.runners.ParentRunner$3.run(ParentRunner.java: 231) atorg.junit.runners.ParentRunner$1.schedule(ParentRunner.java: 60) atorg.junit.runners.ParentRunner.runChildren(ParentRunner.java: 229) atorg.junit.runners.ParentRunner.access$000(ParentRunner.java: 50) atorg.junit.runners.ParentRunner$2.evaluate(ParentRunner.java: 222) atorg.junit.runners.ParentRunner.run(ParentRunner.java: 300) atorg.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java: 45) atorg.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java: 38) atorg.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java: 460) atorg.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java: 673) atorg.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java: 386) atorg.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java: 196) Causedby: org.springframework.beans.factory.BeanCreationException: Couldnotautowirefield: privatecom.spring.model.Tigercom.spring.model.Zoo.tiger;nestedexceptionisorg.springframework.beans.factory.NoSuchBeanDefinitionException: Nomatchingbeanoftype[com.spring.model.Tiger]foundfordependency: expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java: 502) atorg.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java: 84) atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java: 282) ...36more Causedby: org.springframework.beans.factory.NoSuchBeanDefinitionException: Nomatchingbeanoftype[com.spring.model.Tiger]foundfordependency: expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} atorg.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java: 920) atorg.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java: 789) atorg.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java: 703) atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java: 474) ...38more 因为,@Autowired
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- Spring 常用 注解 汇总