Spring注解解析之@ImportResource

之前我们使用spring,最多的还是通过xml配置文件的方式来配置spring bean等内容,随着注解的广泛应用和spring4中Java config的引入,xml配置文件方式逐步被替换,但是如果是想要使用xml配置文件方式的话,也可以通过@ImportResource注解来实现,下面我们来一起看下如何使用.

一、ImportResource

1.1 定义包和类

首先定义一个不会被ComponentScan扫描到的包outpackage，如下：

在该包内创建一个类：

package outpackage; import org.springframework.stereotype.Service; @Service public class HelloService1 { public void method1() { System.out.println("class:HelloService1__method:method1"); } }

1.2 定义配置文件

在资源目录添加配置文件applicationContext.xml：

1.3 定义Java Config类

在启动类平级目录或者是子目录添加java config类保证能够被springboot扫描到，引入xml配置，如下：

package dongshi.daddy; import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.ImportResource; @Configuration @ImportResource({"classpath:applicationContext.xml"}) public class OuterPackageConfiguration { }

1.4 测试代码

@SpringBootApplication public class HelloWorldMainApplication { public static void main(String[] args) throws URISyntaxException, IOException { ConfigurableApplicationContext run = SpringApplication.run(HelloWorldMainApplication.class, args); // 获取通过配置文件定义而被扫描到的类 HelloService1 bean = run.getBean(HelloService1.class); System.out.println(bean); } }

二、运行

2021-05-19 17:52:52.896 INFO 16232 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8083 (http) with context path ''

...snip...

outpackage.HelloService1@1929425f

为了证明确实是xml配置文件在起作用，而不是springboot自己扫描注册，修改配置类，注释掉@ImportResource({"classpath:applicationContext.xml"})，如下：

package dongshi.daddy; import org.springframework.context.annotation.Configuration; @Configuration //@ImportResource({"classpath:applicationContext.xml"}) public class OuterPackageConfiguration { }

然后运行：

2021-05-19 18:01:10.522 INFO 18260 --- [ main] dongshi.daddy.HelloWorldMainApplication : Started HelloWorldMainApplication in 0.944 seconds (JVM running for 1.355)

Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDeFinitionException: No qualifying bean of type 'outpackage.HelloService1' available

at org.springframework.beans.factory.support.DefaultListablebeanfactory.getBean(DefaultListablebeanfactory.java:351)

at org.springframework.beans.factory.support.DefaultListablebeanfactory.getBean(DefaultListablebeanfactory.java:342)

at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1123)

at dongshi.daddy.HelloWorldMainApplication.main(HelloWorldMainApplication.java:16)

可以看到就找不到对应的bean了。