Spring @Value("${property:xxx}") 缺省值

参考：http://www.mkyong.com/spring3/spring-value-default-value/

1. @Value Examples

To set a default value in Spring expression, use Elvis operator :

	#{expression?:default value}

Copy

Few examples :

	@Value("#{systemProperties['mongodb.port'] ?: 27017}")
	private String mongodbPort;

	@Value("#{config['mongodb.url'] ?: '127.0.0.1'}")
	private String mongodbUrl;	
	
	@Value("#{aBean.age ?: 21}")
	private int age;

Copy

P.S @Value has been available since Spring 3.0

2. @Value and Property Examples

To set a default value for property placeholder :

	${property:default value}

Copy

Few examples :

	//@PropertySource("classpath:/config.properties}")
	//@Configuration
	
	@Value("${mongodb.url:127.0.0.1}")
	private String mongodbUrl;
	
	@Value("#{'${mongodb.url:172.0.0.1}'}")
	private String mongodbUrl;
	
	@Value("#{config['mongodb.url']?:'127.0.0.1'}")
	private String mongodbUrl;

Copy

config.properties

mongodb.url=1.2.3.4
mongodb.db=hello

那个 default value，就是前面的property不存在时的默认值。

写个例子测试一下：

app.properties：

last.time=10

spring配置：

	
		
		
			
				classpath:app.properties
			
		
	
	
		
	

测试代码：

	@Value("${last.time:300}")
	private String lastTime;
	
	@Test
	public void test2() {
		System.out.println(lastTime);
	}

输出：10

把app.properties注释

#last.time=10

输出：300