Spring SpEL表达式

定义

Spring 表达式语言(简称SpEL)：是一个支持运行时查询和操作对象图的强大的表达式语言。从Spring3引入了Spring表达式语言（Spring Expression Language,SpEL）。SpEL是一种强大的、简洁的装配Bean的方式，它通过运行期执行的表达式将值装配到Bean的属性或构造器参数中。语法类似于 EL：SpEL 使用 #{...} 作为定界符 , 所有在大括号中的字符都将被认为是 SpEL , SpEL 为 bean 的属性进行动态赋值提供了便利。

通过 SpEL 可以实现：

通过 bean 的 id 对 bean 进行引用。
调用方式以及引用对象中的属性。
计算表达式的值
正则表达式的匹配。

package com.spring.auto.autowire;

public class Car {

    private String brand;
    private double price;
    private String perimeter;

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public String getPerimeter() {
        return perimeter;
    }

    public void setPerimeter(String perimeter) {
        this.perimeter = perimeter;
    }

    @Override
    public String toString() {
        return "Car{" +
                "brand='" + brand + '\'' +
                ", price=" + price +
                ", perimeter='" + perimeter + '\'' +
                '}';
    }
}

package com.spring.auto.autowire;

public class Address {

    private String province;
    private String city;
    private String area;

    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getArea() {
        return area;
    }

    public void setArea(String area) {
        this.area = area;
    }

    @Override
    public String toString() {
        return "Address{" +
                "province='" + province + '\'' +
                ", city='" + city + '\'' +
                ", area='" + area + '\'' +
                '}';
    }
}

package com.spring.auto.autowire;

public class Person {

    private String name;
    private int age;
    private boolean marriage;
    private Car car;
    private String socialStatus;
    private String address;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public boolean isMarriage() {
        return marriage;
    }

    public void setMarriage(boolean marriage) {
        this.marriage = marriage;
    }

    public Car getCar() {
        return car;
    }

    public void setCar(Car car) {
        this.car = car;
    }

    public String getSocialStatus() {
        return socialStatus;
    }

    public void setSocialStatus(String socialStatus) {
        this.socialStatus = socialStatus;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", marriage=" + marriage +
                ", car=" + car +
                ", socialStatus='" + socialStatus + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

package com.spring.auto.autowire;

import com.mchange.v2.c3p0.DataSources;
import com.spring.beans.DataSource;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import java.sql.*;

public class Test {

    public static void main(String[] args) throws SQLException {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("com/spring/auto/autowire/spring_autowire.xml");

        Person person = (Person) applicationContext.getBean("person");
        System.out.println(person);
    }
}

<bean id="car" class="com.spring.auto.autowire.Car">
        <property name="brand" value="#{'玛莎拉蒂'}"></property>
        <property name="price" value="#{32000.78}"></property>
        <property name="perimeter" value="#{T(java.lang.Math).PI * 75.8f}"></property>
    </bean>

    <bean id="person" class="com.spring.auto.autowire.Person">
        <property name='name' value='#{"华崽儿"}'></property>
        <property name="age" value="#{25}"></property>
        <property name="marriage" value="#{car.price > 400000 and age > 30}"></property>
        <property name="car" value="#{car}"></property>
        <property name="socialStatus" value="#{car.price > 30000 ? '金领' : '白领'}"></property>
        <property name="address" value="#{address.province + '省' + address.city + '市' + address.area + '区'}"/>
    </bean>

    <bean id="address" class="com.spring.auto.autowire.Address">
        <property name="province" value="#{'辽宁'}"/>
        <property name="city" value="#{'大连'}"/>
        <property name="area" value="#{'沙河口'}"/>
    </bean>

SpEL 字面量：

整数：<property name="count" value="#{5}"/>
小数：<property name="frequency" value="#{89.7}"/>
科学计数法：<property name="capacity" value="#{1e4}"/>
String可以使用单引号或者双引号作为字符串的定界符号：<property name=“name” value="#{'Chuck'}"/> 或 <property name='name' value='#{"Chuck"}'/>
Boolean：<property name="enabled" value="#{false}"/>

SpEL引用bean , 属性和方法：

SpEL支持的运算符号：

引用其他对象:#{car}
引用其他对象的属性：#{car.brand}
调用其它方法 , 还可以链式操作：#{car.toString()}
调用静态方法或静态属性：通过 T() 调用一个类的静态方法，它将返回一个 Class Object，然后再调用相应的方法或属性：
算数运算符：+, -, *, /, %, ^：
加号还可以用作字符串连接：
比较运算符： <, >, ==, <=, >=, lt, gt, eq, le, ge
逻辑运算符号： and, or, not, | if-else
运算符：?: (ternary), ?: (Elvis)
if-else 的变体
正则表达式：matches

定义

SpEL 字面量：

SpEL引用bean , 属性和方法：

SpEL支持的运算符号：

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