Sping Expression Language -- SpEL, sping expression -- spel

Sping Expression Language -- SpEL, sping expression -- spel

Spring Expression Language --- SpEL
Is a powerful expression language that supports running query and operation objects.
The syntax is similar to EL: SpEL uses # {...} as the separator. All characters in braces will be considered as SpEL.
SpEL facilitates the Dynamic assignment of bean attributes.
With SpEL, you can:
Use the bean id to reference the bean.
Call methods and attributes of referenced objects
Calculate the expression value
Regular Expression matching

SpEL: literal
Literal representation:
-Integer: <property name = "count" value = "# {5}"/>
-Decimal point: <property name = "frequency" value = "# {89.7}"/>
-Scientific Note: <property name = "capacity" value = "# {1e4}"/>
-Single or double quotation marks can be used as the separator of a String: <property name = "name" value = "# {'Tom '}"/> or <property name = "name" value = "# {" Tom "}"/>
-Boolean: <property name = "enabled" value = "# {false}"/>

SpEL: Reference beans, attributes, and methods
Reference other objects
<! -- Configure the application relationship between beans through the value Attribute and SpEL -->
<Property name = "prefix" value = "# {prefixGenerator}"/>
Reference attributes of other objects
<! -- Configure the suffix attribute value as the suffix attribute value of another bean through the value Attribute and SpEL -->
<Property name = "suffix" value = "# {sequenceGenerator2.suffix}"/>
Other methods can be called and chained
<! -- Use the value Attribute and SpEL to configure the suffix property value as the return value of another bean Method -->
<Property name = "suffix" value = "# {sequenceGenerator2.toString ()}"/>
<! -- Method link -->
<Property name = "suffix" value = "# {sequenceGenerator2.toString (). toUpperCase ()}"/>

SpEL: supported Operators
Arithmetic Operators: +,-, *,/, %, ^
The plus sign can also be used as a string connection.
Comparison operators: <,>, =, <=,> =, It, gt, eq, le, ge
Logical operators: and, or, not, |
If-else operator and ternary expression
Regular Expression: matches

Call static methods or static attributes: Call the static method of a Class through T (). It returns a Class Object and then calls the corresponding method or attribute:
<Property name = "initValue" value = "# {T (java. lang. Math). PI}"/>

Sample Code:

1 <? Xml version = "1.0" encoding = "UTF-8"?> 2 <beans xmlns = "http://www.springframework.org/schema/beans" 3 xmlns: xsi = "http://www.w3.org/2001/XMLSchema-instance" 4 xsi: schemaLocation = "http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> 5 6 <bean id = "address" class = "com. yl. spel. address "> 7 <! -- Use SpEL to assign a literal value to the attribute --> 8 <property name = "city" value = "# {'beijing'}"> </property> 9 <property name =" street "value =" # {'wudaokou'} "> </property> 10 </bean> 11 12 <bean id =" car "class =" com. yl. spel. car "> 13 <property name =" brand "value =" Audi "> </property> 14 <property name =" price "value =" 500000 "> </property> 15 <! -- Use SpEL to reference static attributes of the class --> 16 <property name = "tyrePerimeter" value = "# {T (java. lang. math ). PI * 80} "> </property> 17 </bean> 18 19 <bean id =" person "class =" com. yl. spel. person "> 20 <property name =" name "value =" Tom "> </property> 21 <! -- Use SpEL to reference other beans --> 22 <property name = "car" value = "# {car}"> </property> 23 <! -- Use SpEL to reference attributes of other beans --> 24 <property name = "city" value = "# {address. city}"> </property> 25 <! -- Use the SpEL operator --> 26 <property name = "info" value = "# {car. price> 300000? 'Golden limit': 'white-collar '} "> </property> 27 </bean> 28 </beans>