Spring Introductory Lesson Tenth

Spring Expression Language: Spel

The Spring expression language (spel) is a powerful expression language that supports run-time querying and manipulating object graphs.

Syntax similar to El:spel using #{...} As delimiters, all the characters in the curly braces will be considered spel

Spel provides the convenience for dynamic replication of bean properties.

The Spel can be implemented by:

-The bean is referenced by the Bean's ID

-Invoking methods and referencing properties in an object

-evaluates the value of an expression

-Matching of regular expressions

See below how to use

 PackageLogan.spring.study.spel; Public classCar {PrivateString brand; Private intPrice ; Private DoubleTyreperimeter;  PublicString Getbrand () {returnbrand; }     Public voidSetbrand (String brand) { This. Brand =brand; }     Public intGetPrice () {returnPrice ; }     Public voidSetprice (intPrice ) {         This. Price =Price ; }     Public DoubleGettyreperimeter () {returnTyreperimeter; }     Public voidSettyreperimeter (Doubletyreperimeter) {         This. Tyreperimeter =Tyreperimeter; } @Override PublicString toString () {return"Car [brand=" + Brand + ", price=" + Price + ", tyreperimeter=" + Tyreperimeter + "]"; }}

 PackageLogan.spring.study.spel; Public classAddress {PrivateString City; PrivateString Street;  PublicString getcity () {returnCity ; }     Public voidsetcity (String city) { This. City =City ; }     PublicString Getstreet () {returnStreet; }     Public voidSetstreet (String Street) { This. Street =Street; } @Override PublicString toString () {return"Address [city=" + City + ", street=" + Street + "]"; }        }

 PackageLogan.spring.study.spel; Public classPerson {PrivateString name; Privatecar Car; //referencing the city property of the address bean    PrivateString City; //according to the price of car to determine info:car price >=300000 gold collar, otherwise white-collar    PrivateString Info;  PublicString GetName () {returnname; }     Public voidsetName (String name) { This. Name =name; }     PublicCar Getcar () {returncar; }     Public voidSetcar (car car) { This. Car =car; }     PublicString getcity () {returnCity ; }     Public voidsetcity (String city) { This. City =City ; }     PublicString GetInfo () {returninfo; }     Public voidsetInfo (String info) { This. info =info; } @Override PublicString toString () {return"Person [name=" + name + ", car=" + Car + ", city=" + City + ", info=" + info + "]"; }    }

Configuration file

<?XML version= "1.0" encoding= "UTF-8"?><Beansxmlns= "Http://www.springframework.org/schema/beans"Xmlns:xsi= "Http://www.w3.org/2001/XMLSchema-instance"xsi:schemalocation= "Http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd" >        <BeanID= "Address"class= "Logan.spring.study.spel.Address">        <!--use Spel to assign a literal to a property -        < Propertyname= "City"value= "#{' Beijing '}"></ Property>        < Propertyname= "Street"value= "Wudaokou"></ Property>    </Bean>        <BeanID= "Car"class= "Logan.spring.study.spel.Car">        < Propertyname= "Brand"value= "Audi"></ Property>        < Propertyname= "Price"value= "500000"></ Property>        <!--Using Spel to use static properties of a class -        < Propertyname= "Tyreperimeter"value= "#{t (java.lang.Math). PI * +} "></ Property>    </Bean>        <BeanID= "Person"class= "Logan.spring.study.spel.Person">        < Propertyname= "Car"value= "#{car}"></ Property>        < Propertyname= "City"value= "#{address.city}"></ Property>        < Propertyname= "Info"value= "#{car.price > 30?" ' Golden collar ': ' White Collar '} '></ Property>        < Propertyname= "Name"value= "Tom"></ Property>    </Bean></Beans>

 PackageLogan.spring.study.spel;ImportOrg.springframework.context.ApplicationContext;ImportOrg.springframework.context.support.ClassPathXmlApplicationContext; Public classMain { Public Static voidMain (string[] args) {//TODO auto-generated Method StubApplicationContext CTX=NewClasspathxmlapplicationcontext ("Beans-spel.xml"); Address Address= (address) Ctx.getbean ("Address");                SYSTEM.OUT.PRINTLN (address); Car Car= (CAR) ctx.getbean ("Car"));                SYSTEM.OUT.PRINTLN (car); Person Person= (person) ctx.getbean (' person ');    SYSTEM.OUT.PRINTLN (person); }}

Here are the output results

May 10:01:5010:01:50 CST, 10:01:50Class path resource [beans-< c4>spel.xml]address [City =beijing, street=wudaokou]car [Brand=audi, price=500000, tyreperimeter= 251.32741228718345]person [name=tom, Car=car [Brand=audi, price=500000, tyreperimeter=251.32741228718345], city=beijing, info= Gold collar]

Spring Introductory Lesson Tenth