使用@PropertySource读取配置文件通过@Value进行参数注入

project.author=wpfc
project.create_time=2018/3/29

@Configuration
@ComponentScan("cn.edu.ntu")
@PropertySource("classpath:test.properties")
public class ElConfig {
 
    @Value("#{systemProperties['os.name']}")
    private String osName;
    
    //要想使用@Value 用${}占位符注入属性，这个bean是必须的(PropertySourcesPlaceholderConfigurer)，
    //这个就是占位bean,
    //另一种方式是不用value直接用Envirment变量直接getProperty('key')  
    @Value("${project.author}")
    public String author;
    
    @Autowired
    private Environment environment;
    
    //You need this if you use @PropertySource + @Value
    @Bean
    public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
       return new PropertySourcesPlaceholderConfigurer();
    }
    
    public void printProperties(){
        System.out.println("os name : " + osName);
        System.out.println("author  : " + author);
        System.out.println("env     : " + environment.getProperty("project.create_time"));
    }    
}

public class MainApplication {
    public static void main(String[] args){
        AnnotationConfigApplicationContext context = null;
        context = new AnnotationConfigApplicationContext(ElConfig.class);
        ElConfig bean = context.getBean(ElConfig.class);
        bean.printProperties();
    }    
}

    @Value("normal")
    private String normal; // normal (显然这种注入的意义不大)

@Value("#{systemProperties['os.name']}")
    private String systemPropertiesName; 
//效果等同于  是因为spring模版把系统变量否放进了Enviroment
@Value("${os.name}")
    private String systemPropertiesName;

@Value("#{ T(java.lang.Math).random() * 100.0 }")
    private double randomNumber; //41.29185128620939

    @Bean
    public Person person() {
        Person person = new Person();
        person.setName("fangshixiang");
        return person;
    }
 
//注入属性
    @Value("#{person.name}")
    private String personName;
 
    @Test
    public void contextLoads() {
        System.out.println(personName); //fangshixiang
    }

    @Value("classpath:jdbc.properties")
    private Resource resourceFile; // 注入文件资源
 
    @Test
    public void contextLoads() throws IOException {
        System.out.println(resourceFile); //class path resource [jdbc.properties]
        String s = FileUtils.readFileToString(resourceFile.getFile(), StandardCharsets.UTF_8);
        System.out.println(s);
        //输出：
        //db.username=fangshixiang
        //db.password=fang
        //db.url=jdbc:mysql://localhost:3306/mytest
        //db.driver-class-name=com.mysql.jdbc.Driver
    }

    @Value("http://www.baidu.com")
    private Resource testUrl; // 注入URL资源 
 
    @Test
    public void contextLoads() {
        System.out.println(testUrl); //URL [http://www.baidu.com]
    }

    @Value("#{person}")
    private Person value;
 
    @Test
    public void contextLoads() {
        System.out.println(value); //Person(name=fangshixiang, age=null, addr=null, hobby=null)
    }

    @Value("#{person.name}")
    private String personName;
 
    @Value("#{person.age}")
    private String perAge;
 
    //注入默认值
    @Value("#{person.age?:20}")
    private String perAgeDefault;
 
    //如果age22这个key根本就不存在，启动肯定会报错的
    //@Value("#{person.age22?:20}")
    //private String perAgeDefault22;
 
    @Test
    public void contextLoads() {
        System.out.println(personName); //fangshixiang
        System.out.println(perAge); //null
        System.out.println(perAgeDefault); //20
    }

 
    @Value("#{person.parent.name}")
    private String parentName1;
 
    @Value("#{person['parent.name']}")
    private String parentName2;
 
    @Test
    public void contextLoads() {
        System.out.println(parentName1); //fangshixiang
        System.out.println(parentName2); //fangshixiang
    }

    @Value("#{'${os.name}' + '_' +  person.name}")
    private String age; 
 
    @Test
    public void contextLoads() {
        System.out.println(age); //Windows 10_fangshixiang
    }

@Configuration
@PropertySource("classpath:jdbc.properties")
public class PropertySourceConfig {
 
    @Value("${db.url}")
    private String dbUrl;
 
    @PostConstruct
    public void postConstruct() {
        System.out.println(dbUrl); //jdbc:mysql://localhost:3306/mytest
    }
}

	@Override
	public PropertySource<?> createPropertySource(String name, EncodedResource resource) throws IOException {
		return (name != null ? new ResourcePropertySource(name, resource) : new ResourcePropertySource(resource));
	}

@PropertySource(“classpath:jdbc-${spring.profiles.active}.properties”)

@ConfigurationProperties(prefix = "spring.mvc")
public class WebMvcProperties {}
 
//加载方式
	@Configuration
	@Conditional(DefaultDispatcherServletCondition.class)
	@ConditionalOnClass(ServletRegistration.class)
	// 此处采用这个注解，可议把WebMvcProperties这个Bean加载到容器里面去~~~
	// WebMvcProperties里面使用了`@ConfigurationProperties(prefix = "spring.mvc")`
	@EnableConfigurationProperties(WebMvcProperties.class) //加载MVC的配置文件
	protected static class DispatcherServletConfiguration {}

com.example.demo.name=${aaa:hi}
com.example.demo.age=11
com.example.demo.address[0]=北京  # 注意数组 List的表示方式 Map/Obj的方式各位可以自行尝试
com.example.demo.address[1]=上海
com.example.demo.address[2]=广州
com.example.demo.phone.number=1111111

@Component
@ConfigurationProperties(prefix = "com.example.demo")
public class People {
 
    private String name;
    private Integer age;
    private List<String> address;
    private Phone phone;
}   

   @Bean
    @ConfigurationProperties(prefix = "com.example.demo")
    public People people() {
        return new People();
    }

@Component
@PropertySource("classpath:config/object.properties")
@ConfigurationProperties(prefix = "obj")
public class ObjectProperties {}