Spring注解之@ImportResource和@PropertySource分析

清疚 2023-01-22 11:48 172阅读 0赞

## 1：写在前面 ##

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。  
本文基于springboot来进行测试，对springboot不了解或者是想要直接获取测试代码的朋友，可以参考[这篇文章][Link 1]。

## 2：ImportResource ##

### 2.1：定义包和类 ###

首先定义一个不会被`ComponentScan`扫描到的包`outpackage`，如下：  
![在这里插入图片描述][20210519172604623.jpg_pic_center]  
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");
        }
    }

### 2.2：定义配置文件 ###

在资源目录添加配置文件`applicationContext.xml`：

### 2.3：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 { 
    }

### 2.4：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);
        }
    }

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。

## 3：PropertySource ##

该注解的作用和ImportResource作用类似，都是用来引入文件的，只不过ImportResource用来引入xml的配置文件，而PropertySource注解用来引入`properties/yml`的属性文件，一般注入属性值使用。

### 3.1：定义测试bean ###

@Component("myBean")
    @PropertySource("classpath:myPropertySourceBean.properties")
    public class MyPropertySourceBean { 
        @Value("${myBean.name}")
        private String name;
        @Value("${myBean.age}")
        private int age;
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        public int getAge() { 
            return age;
        }
    
        public void setAge(int age) { 
            this.age = age;
        }
    
        @Override
        public String toString() { 
            return "MyPropertySourceBean{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    '}';
        }
    }

### 3.2：定义属性文件 ###

myPropertySourceBean.properties:

myBean.name=jack
    myBean.age=90

### 3.3：测试 ###

@SpringBootApplication
    public class HelloWorldMainApplication { 
    
        public static void main(String[] args) throws URISyntaxException, IOException { 
            ConfigurableApplicationContext run = SpringApplication.run(HelloWorldMainApplication.class, args);
            MyPropertySourceBean bean = run.getBean(MyPropertySourceBean.class);
            System.out.println(bean);
        }
    }

运行：

......
    MyPropertySourceBean{name='jack', age=90}

注意到在bean中还需要配合@Value注解和[SpEL][]来注入值，针对这点springboot引入了@ConfigurationProperties注解来自动注入属性值，优化如下：

@Component("myBean")
    @PropertySource("classpath:myPropertySourceBean.properties")
    @ConfigurationProperties(prefix = "mybean")
    public class MyPropertySourceBean { 
    // @Value("${myBean.name}")
        private String name;
    // @Value("${myBean.age}")
        private int age;
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        public int getAge() { 
            return age;
        }
    
        public void setAge(int age) { 
            this.age = age;
        }
    
        @Override
        public String toString() { 
            return "MyPropertySourceBean{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    '}';
        }
    }

增加了`@ConfigurationProperties(prefix = "mybean")`，删除了`@Value`相关注解，运行效果不变，大家可以试下。

[Link 1]: https://blog.csdn.net/wang0907/article/details/110478990
[20210519172604623.jpg_pic_center]: /images/20221020/d7f7833a39604651bffcedc34b447517.png
[SpEL]: https://blog.csdn.net/wang0907/article/details/116453128