Spring Configuration (iii): Expression language for spring el--spring

Spring el--spring Expression language:
Supports the use of expressions in XML and annotations, similar to the El Expression language of JSPs.
Spring development often involves invoking a variety of resources, including common files, URLs, configuration files, system environment variables, and so on, and we might use spring's expression language to implement resource injection.
Spring uses an expression primarily in @value parameters.
Example:
Inject normal string:
@Value ("Hello.") I Love you. ")
Private String normal;


Inject Operating System Properties:
@Value ("#{systemproperties[' Os.name ']}")
Private String Osname;


The result of the injection expression operation:
@Value ("#{T (Java.lang.Math). Random () * 100.0}")
Private double random number


Inject the properties of another bean
@Value ("#{demoservice.another}")
Private String Fromanother


Inject file contents
@Value ("Classpath:com/wisely/highlight_spring4/ch2/el/test.txt")
Private Resource Testfile


Inject URL
@Value ("http://www.baidu.com")
Private Resource Testurl


Inject property file: Use @propertysource ("classpath:com/wisely/"). /test.properties ") Specifies the property file
@Value ("${book.name}")
Private String BookName