spring Integration中的表达式调用类的方法的处理方法 spring el表达式解析

1：写在前面

spring在spring3版本后提供了el表达式的功能，表达式的计算，对象的访问，方法的调用等。对应的顶层接口是org.springframework.expression.ExpressionParser。

2：字符串常量作为表达式

2.1：测试代码

public static void stringContantExp() {
    // 定义表达式解析器对象
    ExpressionParser expressionParser = new SpelExpressionParser();
    // 设置字符串常量的表达式，'test spring el'就是我们定义的表达式，只不过这里是一个字符串的常量
    Expression expression = expressionParser.parseExpression("'test spring el'");
    // 获取表达式的值
    String value = (String) expression.getValue();
    System.out.println("表达式的值是：" + value);

    // 设置调用字符串普通方法的EL表达式
    expression = expressionParser.parseExpression("'test spring el'.charAt(0)");
    System.out.println("通过表达式访问对象普通方法获取的值是：" + expression.getValue());

    // 设置调用字符串get方法的EL表达式
    expression = expressionParser.parseExpression("'test spring el'.getClass()");
    System.out.println("通过表达式访问对象get方法获取的值是：" + expression.getValue());

    // 通过EL访问属性
    expression = expressionParser.parseExpression("'test spring el'.bytes.length");
    System.out.println("通过表达式访问属性的值是：" + expression.getValue());
}

2.2：运行

表达式的值是：test spring el
通过表达式访问对象普通方法获取的值是：t
通过表达式访问对象get方法获取的值是：class java.lang.String
通过表达式访问属性的值是：14

3：操作对象的属性

3.1：测试代码

public class Role2{

    //赋值long型
    private Long id;
    //字符串赋值
    private String roleName;
    //字符串赋值
    private String note;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getRoleName() {
        return roleName;
    }

    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }

    public String getNote() {
        return note;
    }

    public void setNote(String note) {
        this.note = note;
    }

    public Role2(long l, String role_name, String note) {
        this.id = l;
        this.roleName = role_name;
        this.note = note;
    }

    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
}

public static void testObjPropEl() {
     /* 从根对象中读取属性开始 */
     // 表达式解析器
     ExpressionParser parser = new SpelExpressionParser();
     // 定义根对象
     Role2 role = new Role2(1L, "role_name", "note");
     // 定义要访问的属性note的表达式
     Expression exp = parser.parseExpression("note");
     // 从根对象role中访问属性note
     String note = (String) exp.getValue(role);
     System.out.println(note);
     /* 从根对象中读取属性结束 */

     /* 设置根对象属性开始 */
     // 使用role作为根对象创建计算上下文对象
     EvaluationContext ctx = new StandardEvaluationContext(role);
     // 设置根对象的note属性的值为new_note
     parser.parseExpression("note").setValue(ctx, "new_note");
     // 获取根对象的note属性的值，并指定以String类型返回
     note = parser.parseExpression("note").getValue(ctx, String.class);
     System.out.println(note);
     /* 设置根对象属性结束 */

     /* 调用根对象的getRoleName方法开始 */
     // 调用getRoleName方法
     String roleName = parser.parseExpression("getRoleName()").getValue(ctx, String.class);
     System.out.println(roleName);
     /* 调用根对象的getRoleName方法结束 */
 }

3.2：运行

note
new_note
role_name

4：操作集合

4.1：测试代码

private static void testListEl() {
    ExpressionParser parser = new SpelExpressionParser();
    List<String> list = new ArrayList<>();
    list.add("value-0");
    list.add("value-1");
    // 创建上下文，并将集合设置到上下文中
    EvaluationContext ctx = new StandardEvaluationContext();
    ctx.setVariable("list", list);
    // 获取索引位置1的值
    String pos1El = "#list[1]";
    String value = parser.parseExpression(pos1El).getValue(ctx, String.class);
    System.out.println("索引位置1的值是：" + value);
    // 设置索引位置0的值为新值
    String pos0El = "#list[0]";
    parser.parseExpression(pos0El).setValue(ctx, "new-value-0");
    value = parser.parseExpression(pos0El).getValue(ctx, String.class);
    System.out.println("索引位置0的新值是：" + value);
}

4.2：运行

索引位置1的值是：value-1
索引位置0的新值是：new-value-0

5：基于EL表达式创建bean(xml)

5.1：类

public class Item {

    private String name;
    private int total;

    public String getName() {
        return name;
    }

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

    public int getTotal() {
        return total;
    }

    public void setTotal(int total) {
        this.total = total;
    }

    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
}

public class Customer {

    private Item item;
    private String itemName;

    public Item getItem() {
        return item;
    }

    public void setItem(Item item) {
        this.item = item;
    }

    public String getItemName() {
        return itemName;
    }

    public void setItemName(String itemName) {
        this.itemName = itemName;
    }

    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
}

5.2：配置文件

<?xml version="1.0" encoding="UTF-8"?>
<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.xsd">
    <bean id="itemBean" class="yudaosourcecode.speltest.Item">
        <property name="name" value="itemA" />
        <property name="total" value="10" />
    </bean>

    <bean id="customerBean" class="yudaosourcecode.speltest.Customer">
        <property name="item" value="#{itemBean}" />
        <property name="itemName" value="#{itemBean.name}" />
    </bean>
</beans>

5.3：测试代码

@Test
publicvoid createbeanwitheltest() {
    ClassPathXmlApplicationContext ac
            = new ClassPathXmlApplicationContext("speltest/createbeanwitheltest.xml");
    System.out.println(ac.getBean("customerBean"));
}

5.4：运行

{"item":{"name":"itemA","total":10},"itemName":"itemA"}

6：基于EL表达式创建bean(annotation)

6.1：类

@Component("itemBean")
public class Item {

    @Value("itemA_byannotation")//直接注入String
    private String name;
    
    @Value("102")//直接注入integer
    private int total;

    public String getName() {
        return name;
    }

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

    public int getTotal() {
        return total;
    }

    public void setTotal(int total) {
        this.total = total;
    }

    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
}

@Component("customerBean")
public class Customer {

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

    public Item getItem() {
        return item;
    }

    public void setItem(Item item) {
        this.item = item;
    }

    public String getItemName() {
        return itemName;
    }

    public void setItemName(String itemName) {
        this.itemName = itemName;
    }

    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
}

6.2：配置文件

<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="yudaosourcecode.speltest.byannotation" />
</beans>

6.3：测试类

@Test
public void createbeanwithelannotationtest() {
    ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("speltest/createbeanwithelannotationtest.xml");
    System.out.println(ac.getBean("customerBean"));
}

6.4：运行

{"item":{"name":"itemA_byannotation","total":102},"itemName":"itemA_byannotation"}

7：基于方法调用创建bean(annotation)

7.1：类

@Component("customerBean")
public class Customer {

    // 调用toUpperCase方法将lei转大写设置为值
    @Value("#{'lei'.toUpperCase()}")
    private String name;

    // 调用名称为priceBean的getSpecialPrice方法作为amount的值
    @Value("#{priceBean.getSpecialPrice()}")
    private double amount;

    public String getName() {
        return name;
    }

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

    public double getAmount() {
        return amount;
    }

    public void setAmount(double amount) {
        this.amount = amount;
    }

    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
}

@Component("priceBean")
public class Price {
 
    public double getSpecialPrice() {
        return new Double(99.99);
    }
}

7.2：配置文件

<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="yudaosourcecode.speltest.bymethodinvovationannotation" />
</beans>

7.3：测试代码

@Test
public void bymethodinvovationannotation() {
    ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("speltest/bymethodinvovationannotation.xml");
    System.out.println(ac.getBean("customerBean"));
}

7.4：运行

{"amount":99.99,"name":"LEI"}

8：基于方法调用创建bean(xml)

8.1：类

public class Customer {

    private String name;

    private double amount;

    public String getName() {
        return name;
    }

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

    public double getAmount() {
        return amount;
    }

    public void setAmount(double amount) {
        this.amount = amount;
    }

    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
}

public class Price {
 
    public double getSpecialPrice() {
        return new Double(66.99);
    }
}

8.2：配置文件

<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="yudaosourcecode.speltest.bymethodinvovationxml.Customer
">
        <property name="name" value="#{'dongshidaddy'.toUpperCase()}" />
        <property name="amount" value="#{priceBean.getSpecialPrice()}" />
    </bean>

    <bean id="priceBean" class="yudaosourcecode.speltest.bymethodinvovationxml.Price" />

</beans>

8.3：测试代码

@Test
public void bymethodinvovationxml() {
    ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("speltest/bymethodinvovationxml.xml");
    System.out.println(ac.getBean("customerBean"));
}

8.4：运行

{"amount":66.99,"name":"DONGSHIDADDY"}

9：运算符

9.1：类

@Component("customerBean")
public class MyOperatorBean {

    @Value("#{1 == 1}") //true
    private boolean testEqual;

    @Value("#{1 != 1}") //false
    private boolean testNotEqual;

    @Value("#{numberBean.no == 999 and numberBean.no < 900}") //false
    private boolean testAnd;

    @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("#{2 ^ 2}") //4.0
    private double testExponentialPower;

    // 三目
    @Value("#{20 < 100 ? true : false}")
    private boolean warning;

	...snip getter and setter...
	
    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
}

@Component("numberBean")
public class Number {
 
    @Value("999")
    private int no;
 
    public int getNo() {
        return no;
    }
 
    public void setNo(int no) {
        this.no = no;
    }
 
}

9.2：配置文件

<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="yudaosourcecode.speltest.eloperatortest" />
</beans>

9.3：测试类

@Test
public void eloperatortest() {
    ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("speltest/eloperatortest.xml");
    System.out.println(ac.getBean("customerBean"));
}

9.4：运行

{"testAddString":"1@1","testAnd":false,"testDivision":5.0,"testEqual":true,"testExponentialPower":4.0,"testMultiplication":1.0,"testNotEqual":false,"testSubtraction":0.0,"warning":true}