spring of spring expression language: SpEL

(1) spring expression language is a support query and manipulate an object graph I have a strong expression language runtime.

(2) language similar EL: SpEL using # {...} as delimiters. All strings in braces are considered SpEL.

(3) SpEL dynamically assigned to the bean property provides convenient.

(4) can be achieved by SpEL:

Make reference to Bean by Bean's id
Call methods and properties referenced object
Value calculation expression
Regular expression match

Literal representation:

Integer: # {5}
Decimal: # {3.45}
Scientific notation: # [1e4]
String: may be used single or double quotes delimiter early taste string: # { 'tom'}, # { "tom"}
Boolean: # {false}

SpEL support operation symbol: + - * /% ^ <> == <=> = lt gt eq le ge and or not | (:) if-else like a regular expression?

Call static properties and methods: by T ()

The following codes are ignored class getter, setter and to_string method.

Car.java

package com.gong.spring.beans.spel;

public class Car {
    
    public Car() {
    }

    public Car(String name) {
        this.name = name;
    }
    private String name;
    //轮胎周长
    private double tyrePerimeter;
    private double price;
}

Address.java

package com.gong.spring.beans.spel;

public class Address {
    private String city;
    private String street;
}

Student.java

package com.gong.spring.beans.spel;

public class Student {
    
    private String name;
    private int age;
    private double score;
    private String city;
    private String info;
    private Car car;
    private Address address;
}

Beans spel.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="car" class="com.gong.spring.beans.spel.Car" p:name="baoma"
　　 p:tyrePerimeter="#{T(java.lang.Math).PI*80}"></bean>
    <bean id="address" class="com.gong.spring.beans.spel.Address" 
    p:city="武汉" p:street="#{'络南街道'}"></bean>

    <bean id="student" class="com.gong.spring.beans.spel.Student" p:name="tom"
    p:age="#{12}" p:score="#{99.00}"> 
        <!-- 使用spel引用其它的bean -->
        <property name="car" value="#{car}"></property>
        <!- nameProperty<->Use spel reference other attributes bean
        = "City" value = "# {} address.city" > </ Property > 
        <-! Use spel operator, dynamic evaluation -> 
        < Property name = "info" value = "# {car.price> ? 300000 'rich': 'money'} " > </ Property > 
    </ the bean > 

</ Beans >

Main.java

package com.gong.spring.beans.spel;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {
        //1.创建spring的IOC容器对象
        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-spel.xml");
        //2.从容器中获取Bean实例
        Student student = (Student) ctx.getBean("student");
        System.out.println(student.toString());
    }
}

Part of the output:

spring of spring expression language: SpEL

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