Spring3系列6-Spring 表达式语言(Spring EL)

本篇讲述了Spring Expression Language —— 即Spring3中功能丰富强大的表达式语言，简称SpEL。SpEL是类似于OGNL和JSF EL的表达式语言，能够在运行时构建复杂表达式，存取对象属性、对象方法调用等。所有的SpEL都支持XML和Annotation两种方式，格式：#{ SpEL expression }

一、第一个Spring EL例子—— HelloWorld Demo

这个例子将展示如何利用SpEL注入String、Integer、Bean到属性中。

1. Spring El的依赖包

首先在Maven的pom.xml中加入依赖包，这样会自动下载SpEL的依赖。

文件：pom.xml

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>3.2.4.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>3.2.4.RELEASE</version>
    </dependency>
  </dependencies>

2. Spring Bean

接下来写两个简单的Bean，稍后会用SpEL注入value到属性中。

Item.java如下：

package com.lei.demo.el;

public class Item {

    private String name;
    private int total;
    
    //getter and setter...
}

Customer.java如下：

package com.lei.demo.el;

public class Customer {

    private Item item;
    private String itemName;

　　@Override
    public String toString() {
　　return "itemName=" +this.itemName+" "+"Item.total="+this.item.getTotal();
    }
    
    //getter and setter...

}

3. Spring EL——XML

SpEL格式为#{ SpEL expression }，xml配置见下。

文件：Spring-EL.xml

<beans xmlns="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-3.0.xsd">
 
    <bean id="itemBean" class="com.lei.demo.el.Item">
        <property name="name" value="itemA" />
        <property name="total" value="10" />
    </bean>
 
    <bean id="customerBean" class="com.lei.demo.el.Customer">
        <property name="item" value="#{itemBean}" />
        <property name="itemName" value="#{itemBean.name}" />
    </bean>
 
</beans>

注解：

1. #{itemBean}——将itemBean注入到customerBean的item属性中。

2. #{itemBean.name}——将itemBean 的name属性，注入到customerBean的属性itemName中。

4. Spring EL——Annotation

SpEL的Annotation版本。

注意：要在Annotation中使用SpEL，必须要通过annotation注册组件。如果你在xml中注册了bean和在java class中定义了@Value，@Value在运行时将失败。

Item.java如下：

package com.lei.demo.el;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component("itemBean")
public class Item {

    @Value("itemA")//直接注入String
    private String name;
    
    @Value("10")//直接注入integer
    private int total;
    
    //getter and setter...
}

Customer.java如下：

package com.lei.demo.el;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component("customerBean")
public class Customer {

    @Value("#{itemBean}")
    private Item item;
    
    @Value("#{itemBean.name}")
    private String itemName;
    
　　//getter and setter...
}

Xml中配置组件自动扫描

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-3.0.xsd">
 
    <context:component-scan base-package="com.lei.demo.el" />
 
</beans>

在Annotation模式中，用@Value定义EL。在这种情况下，直接注入一个String和integer值到itemBean中，然后注入itemBean到customerBean中。

5. 输出结果

App.java如下：

package com.lei.demo.el;

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

public class App {

    public static void main(String[] args) {

        ApplicationContext context = new ClassPathXmlApplicationContext("Spring-EL.xml");
         
        Customer obj = (Customer) context.getBean("customerBean");
        System.out.println(obj);

    }

}

输出结果如下：itemName=itemA item.total=10

二、 Spring EL Method Invocation——SpEL 方法调用

SpEL允许开发者用El运行方法函数，并且允许将方法返回值注入到属性中。

1. Spring EL Method Invocation之Annotation

此段落演示用@Value注释，完成SpEL方法调用。

Customer.java如下：

package com.lei.demo.el;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
 
@Component("customerBean")
public class Customer {
 
    @Value("#{'lei'.toUpperCase()}")
    private String name;
 
    @Value("#{priceBean.getSpecialPrice()}")
    private double amount;
    
    //getter and setter...省略
 
    @Override
    public String toString() {
        return "Customer [name=" + name + ", amount=" + amount + "]";
    }
 
}

Price.java如下：

package com.lei.demo.el;
 
import org.springframework.stereotype.Component;
 
@Component("priceBean")
public class Price {
 
    public double getSpecialPrice() {
        return new Double(99.99);
    }
 
}

输出结果：Customer[name=LEI,amount=99.99]

上例中，以下语句调用toUpperCase()方法

@Value("#{'lei'.toUpperCase()}")
private String name;

上例中，以下语句调用priceBean中的getSpecialPrice()方法

@Value("#{priceBean.getSpecialPrice()}")
private double amount;

2. Spring EL Method Invocation之XML

在XMl中配置如下，效果相同

<beans xmlns="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-3.0.xsd">
 
    <bean id="customerBean" class="com.leidemo.el.Customer">
        <property name="name" value="#{'lei'.toUpperCase()}" />
        <property name="amount" value="#{priceBean.getSpecialPrice()}" />
    </bean>
 
    <bean id="priceBean" class="com.lei.demo.el.Price" />
 
</beans>

三、 Spring EL Operators——SpEL 操作符

　　Spring EL 支持大多数的数学操作符、逻辑操作符、关系操作符。

　　1.关系操作符

　　包括：等于 (==, eq)，不等于 (!=, ne)，小于 (<, lt),，小于等于(<= , le)，大于(>, gt)，大于等于 (>=, ge)

　　2.逻辑操作符

　　包括：and，or，and not(!)

　　3.数学操作符

　　包括：加 (+)，减 (-)，乘 (*)，除 (/)，取模 (%)，幂指数 (^)。

1. Spring EL Operators之Annotation

Numer.java如下

package com.lei.demo.el;
 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
 
@Component("numberBean")
public class Number {
 
    @Value("999")
    private int no;
 
    public int getNo() {
        return no;
    }
 
    public void setNo(int no) {
        this.no = no;
    }
 
}

Customer.java如下

package com.lei.demo.el;
 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
 
@Component("customerBean")
public class Customer {
 
    //Relational operators
 
    @Value("#{1 == 1}") //true
    private boolean testEqual;
 
    @Value("#{1 != 1}") //false
    private boolean testNotEqual;
 
    @Value("#{1 < 1}") //false
    private boolean testLessThan;
 
    @Value("#{1 <= 1}") //true
    private boolean testLessThanOrEqual;
 
    @Value("#{1 > 1}") //false
    private boolean testGreaterThan;
 
    @Value("#{1 >= 1}") //true
    private boolean testGreaterThanOrEqual;
 
    //Logical operators , numberBean.no == 999
 
    @Value("#{numberBean.no == 999 and numberBean.no < 900}") //false
    private boolean testAnd;
 
    @Value("#{numberBean.no == 999 or numberBean.no < 900}") //true
    private boolean testOr;
 
    @Value("#{!(numberBean.no == 999)}") //false
    private boolean testNot;
 
    //Mathematical operators
 
    @Value("#{1 + 1}") //2.0
    private double testAdd;
 
    @Value("#{'1' + '@' + '1'}") //1@1
    private String testAddString;
 
    @Value("#{1 - 1}") //0.0
    private double testSubtraction;
 
    @Value("#{1 * 1}") //1.0
    private double testMultiplication;
 
    @Value("#{10 / 2}") //5.0
    private double testDivision;
 
    @Value("#{10 % 10}") //0.0
    private double testModulus ;
 
    @Value("#{2 ^ 2}") //4.0
    private double testExponentialPower;
 
    @Override
    public String toString() {
        return "Customer [testEqual=" + testEqual + ", testNotEqual="
                + testNotEqual + ", testLessThan=" + testLessThan
                + ", testLessThanOrEqual=" + testLessThanOrEqual
                + ", testGreaterThan=" + testGreaterThan
                + ", testGreaterThanOrEqual=" + testGreaterThanOrEqual
                + ", testAnd=" + testAnd + ", testOr=" + testOr + ", testNot="
                + testNot + ", testAdd=" + testAdd + ", testAddString="
                + testAddString + ", testSubtraction=" + testSubtraction
                + ", testMultiplication=" + testMultiplication
                + ", testDivision=" + testDivision + ", testModulus="
                + testModulus + ", testExponentialPower="
                + testExponentialPower + "]";
    }
 
}

运行如下代码：

Customer obj = (Customer) context.getBean("customerBean");
System.out.println(obj);

结果如下：

Customer [
    testEqual=true, 
    testNotEqual=false, 
    testLessThan=false, 
    testLessThanOrEqual=true, 
    testGreaterThan=false, 
    testGreaterThanOrEqual=true, 
    testAnd=false, 
    testOr=true, 
    testNot=false, 
    testAdd=2.0, 
    testAddString=1@1, 
    testSubtraction=0.0, 
    testMultiplication=1.0, 
    testDivision=5.0, 
    testModulus=0.0, 
    testExponentialPower=4.0
]

2. Spring EL Operators之XML

以下是等同的xml配置。

注意，类似小于号“<”，或者小于等于“<=”，在xml中是不直接支持的，必须用等同的文本表示方法表示，

例如，“<”用“lt”替换；“<=”用“le”替换，等等。

<beans xmlns="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-3.0.xsd">
 
    <bean id="customerBean" class="com.lei.demo.el.Customer">
 
      <property name="testEqual" value="#{1 == 1}" />
      <property name="testNotEqual" value="#{1 != 1}" />
      <property name="testLessThan" value="#{1 lt 1}" />
      <property name="testLessThanOrEqual" value="#{1 le 1}" />
      <property name="testGreaterThan" value="#{1 > 1}" />
      <property name="testGreaterThanOrEqual" value="#{1 >= 1}" />
 
      <property name="testAnd" value="#{numberBean.no == 999 and numberBean.no lt 900}" />
      <property name="testOr" value="#{numberBean.no == 999 or numberBean.no lt 900}" />
      <property name="testNot" value="#{!(numberBean.no == 999)}" />
 
      <property name="testAdd" value="#{1 + 1}" />
      <property name="testAddString" value="#{'1' + '@' + '1'}" />
      <property name="testSubtraction" value="#{1 - 1}" />
      <property name="testMultiplication" value="#{1 * 1}" />
      <property name="testDivision" value="#{10 / 2}" />
      <property name="testModulus" value="#{10 % 10}" />
      <property name="testExponentialPower" value="#{2 ^ 2}" />
 
    </bean>
 
    <bean id="numberBean" class="com.lei.demo.el.Number">
        <property name="no" value="999" />
    </bean>
 
</beans>

四、 Spring EL 三目操作符condition?true:false

SpEL支持三目运算符，以此来实现条件语句。

1. Annotation

Item.java如下：

package com.lei.demo.el;
 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
 
@Component("itemBean")
public class Item {
 
    @Value("99")
    private int qtyOnHand;
 
    public int getQtyOnHand() {
        return qtyOnHand;
    }
 
    public void setQtyOnHand(int qtyOnHand) {
        this.qtyOnHand = qtyOnHand;
    }
 
}

Customer.java如下：

package com.lei.demo.el;
 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
 
@Component("customerBean")
public class Customer {
 
    @Value("#{itemBean.qtyOnHand < 100 ? true : false}")
    private boolean warning;
 
    public boolean isWarning() {
        return warning;
    }
 
    public void setWarning(boolean warning) {
        this.warning = warning;
    }
 
    @Override
    public String toString() {
        return "Customer [warning=" + warning + "]";
    }
 
}

输出：Customer [warning=true]

2. XMl

Xml配置如下，注意：应该用“&lt；”代替小于号“<”

<beans xmlns="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-3.0.xsd">
 
    <bean id="customerBean" class="com.lei.demo.el.Customer">
        <property name="warning" 
                          value="#{itemBean.qtyOnHand &lt; 100 ? true : false}" />
    </bean>
 
    <bean id="itemBean" class="com.lei.demo.el.Item">
        <property name="qtyOnHand" value="99" />
    </bean>
 
</beans>

输出：Customer [warning=true]

五、 Spring EL 操作List、Map集合取值

此段演示SpEL怎样从List、Map集合中取值，简单示例如下：

    //get map where key = 'MapA'
    @Value("#{testBean.map['MapA']}")
    private String mapA;
 
    //get first value from list, list is 0-based.
    @Value("#{testBean.list[0]}")
    private String list;

1. Annotation

首先，创建一个HashMap和ArrayList，并初始化一些值。

Test.java如下：

package com.lei.demo.el;
 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.springframework.stereotype.Component;
 
@Component("testBean")
public class Test {
 
    private Map<String, String> map;
    private List<String> list;
 
    public Test() {
        map = new HashMap<String, String>();
        map.put("MapA", "This is A");
        map.put("MapB", "This is B");
        map.put("MapC", "This is C");
 
        list = new ArrayList<String>();
        list.add("List0");
        list.add("List1");
        list.add("List2");
 
    }
 
    public Map<String, String> getMap() {
        return map;
    }
 
    public void setMap(Map<String, String> map) {
        this.map = map;
    }
 
    public List<String> getList() {
        return list;
    }
 
    public void setList(List<String> list) {
        this.list = list;
    }
 
}

然后，用SpEL取值，Customer.java如下

package com.lei.demo.el;
 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
 
@Component("customerBean")
public class Customer {
 
    @Value("#{testBean.map['MapA']}")
    private String mapA;
 
    @Value("#{testBean.list[0]}")
    private String list;
 
    public String getMapA() {
        return mapA;
    }
 
    public void setMapA(String mapA) {
        this.mapA = mapA;
    }
 
    public String getList() {
        return list;
    }
 
    public void setList(String list) {
        this.list = list;
    }
 
    @Override
    public String toString() {
        return "Customer [mapA=" + mapA + ", list=" + list + "]";
    }
 
}

调用代码如下：

Customer obj = (Customer) context.getBean("customerBean");
System.out.println(obj);

输出结果：Customer [mapA=This is A, list=List0]

2. XML

Xml配置如下：

<beans xmlns="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-3.0.xsd">
 
    <bean id="customerBean" class="com.lei.demo.el.Customer">
        <property name="mapA" value="#{testBean.map['MapA']}" />
        <property name="list" value="#{testBean.list[0]}" />
    </bean>
 
    <bean id="testBean" class="com.lei.demo.el.Test" />
 
</beans>

posted @ 2016-01-22 09:43 门罗的魔术师阅读(246) 评论(0) 编辑收藏举报

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魔术师

Spring3系列6-Spring 表达式语言(Spring EL)

一、 第一个Spring EL例子—— HelloWorld Demo

二、 Spring EL Method Invocation——SpEL 方法调用

三、 Spring EL Operators——SpEL 操作符

四、 Spring EL 三目操作符condition?true:false

五、 Spring EL 操作List、Map集合取值

一、 第一个Spring EL例子—— HelloWorld Demo

二、 Spring EL Method Invocation——SpEL 方法调用

1. Spring EL Method Invocation之Annotation

2. Spring EL Method Invocation之XML

三、 Spring EL Operators——SpEL 操作符

1. Spring EL Operators之Annotation

2. Spring EL Operators之XML

四、 Spring EL 三目操作符condition?true:false

1. Annotation

2. XMl

五、 Spring EL 操作List、Map集合取值

1. Annotation

2. XML

公告

一、第一个Spring EL例子—— HelloWorld Demo

一、第一个Spring EL例子—— HelloWorld Demo