SpringBoot底层注解
1. @Configuration详解
基本使用
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@Configuration(proxyBeanMethods = false)
public class MyConfig {
@Bean
public User user01(){
User zhangsan = new User("zhangsan", 18);
zhangsan.setPet(tomcatPet());
return zhangsan;
}
@Bean("tom")
public Pet tomcatPet(){
return new Pet("tomcat");
}
}
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- 最佳实战
- 配置 类组件之间无依赖关系用Lite模式加速容器启动过程，减少判断
- 配置 类组件之间有依赖关系，方法会被调用得到之前单实例组建，用Full模式（默认）
2. @Import导入组件
@Bean、@Component、@Controller、@Service、@Repository，它们是Spring的基本标签，在Spring Boot中并未改变它们原来的功能。
@Import({User.class, DBHelper.class})给容器中自动创建出这两个类型的组件、默认组件的名字就是全类名
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| @Import({User.class, DBHelper.class})
@Configuration(proxyBeanMethods = false)
public class MyConfig {
}
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测试类：
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ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
String[] beanNamesForType = run.getBeanNamesForType(User.class);
for (String s : beanNamesForType) {
System.out.println(s);
}
DBHelper bean1 = run.getBean(DBHelper.class);
System.out.println(bean1);
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3. @Conditional条件装配
条件装配：满足Conditional制定的条件，则进行组件注入
用@ConditionalOnMissingBean举例说明
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| @Configuration(proxyBeanMethods = false)
@ConditionalOnMissingBean(name = "tom")
public class MyConfig {
@Bean
public User user01(){
User zhangsan = new User("zhangsan", 18);
zhangsan.setPet(tomcatPet());
return zhangsan;
}
@Bean("tom22")
public Pet tomcatPet(){
return new Pet("tomcat");
}
}
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
String[] names = run.getBeanDefinitionNames();
for (String name : names) {
System.out.println(name);
}
boolean tom = run.containsBean("tom");
System.out.println("容器中Tom组件："+tom);
boolean user01 = run.containsBean("user01");
System.out.println("容器中user01组件："+user01);
boolean tom22 = run.containsBean("tom22");
System.out.println("容器中tom22组件："+tom22);
}
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4. @ImportResource导入Spring配置文件
比如，公司使用bean.xml文件生成配置bean，然而你为了省事，想继续复用bean.xml，@ImportResource粉墨登场。
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| <?xml version="1.0" encoding="UTF-8"?>
<beans ...">
<bean id="haha" class="com.lun.boot.bean.User">
<property name="name" value="zhangsan"></property>
<property name="age" value="18"></property>
</bean>
<bean id="hehe" class="com.lun.boot.bean.Pet">
<property name="name" value="tomcat"></property>
</bean>
</beans>
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使用方法：
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| @ImportResource("classpath:beans.xml")
public class MyConfig {
...
}
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测试：
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| public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
boolean haha = run.containsBean("haha");
boolean hehe = run.containsBean("hehe");
System.out.println("haha："+haha);
System.out.println("hehe："+hehe);
}
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5. ConfigurationProperties配置绑定
如何使用Java读取到properties文件中的内容，并且把它封装到JavaBean中，以供随时使用
老方法：
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| public class getProperties {
public static void main(String[] args) throws FileNotFoundException, IOException {
Properties pps = new Properties();
pps.load(new FileInputStream("a.properties"));
Enumeration enum1 = pps.propertyNames();
while(enum1.hasMoreElements()) {
String strKey = (String) enum1.nextElement();
String strValue = pps.getProperty(strKey);
System.out.println(strKey + "=" + strValue);
}
}
}
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Spring Boot一种配置配置绑定：
@ConfigurationProperties + @Component
假设有配置文件application.properties
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| mycar.brand=BYD
mycar.price=100000
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只有在容器中的组件，才会拥有SpringBoot提供的强大功能
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| @Component
@ConfigurationProperties(prefix = "mycar")
public class Car {
...
}
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Spring Boot另一种配置配置绑定：
@EnableConfigurationProperties + @ConfigurationProperties
- 开启Car配置绑定功能
- 把Car这个组件自动注册到容器中
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| @EnableConfigurationProperties(Car.class)
public class MyConfig {
...
}
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| @ConfigurationProperties(prefix = "mycar")
public class Car {
...
}
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