Spring @Value("${property:xxx}") 缺省值

参考：/spring3/spring-value-default-value/

1. @Value Examples

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

	#{expression?:default value}

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Few examples :

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

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

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 @Value has been available since Spring 3.0

2. @Value and Property Examples

To set a default value for property placeholder :

	${property:default value}

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Few examples :

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

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=1.2.3.4
=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：

：

=10

spring配置：

	<bean 
		class="">
		<property name="fileEncoding" value="UTF-8" />
		<property name="locations">
			<list>
				<value>classpath:</value>
			</list>
		</property>
	</bean>
	<bean 
		class="">
		<property name="properties" ref="configProperties" />
	</bean>

测试代码：

	@Value("${:300}")
	private String lastTime;
	
	@Test
	public void test2() {
		(lastTime);
	}

输出：10

把注释

#=10

输出：300