Spring的属性依赖检查

spring支持4种依赖检查：默认的是none

• none – No dependency checking.
• simple – If any properties of primitive type (int, long,double…) and collection types (map, list..) have not been set, UnsatisfiedDependencyException will be thrown.
• objects – If any properties of object type have not been set, UnsatisfiedDependencyException will be thrown.
• all – If any properties of any type have not been set, an UnsatisfiedDependencyException will be thrown.

 举个例子

    public class Customer  
    {  
        private Person person;  
        private int type;  
        private String action;  
        
        //getter and setter methods  
    }  

    public class Person  
    {  
        private String name;  
        private String address;  
        private int age;  
        
        //getter and setter methods  
    }  

1. none dependency checking

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    <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-2.5.xsd">  
        
        <bean id="CustomerBean" class="com.mkyong.common.Customer" >  
            <property name="action" value="buy" />  
        </bean>  
        
        <bean id="PersonBean" class="com.mkyong.common.Person">  
            <property name="name" value="mkyong" />  
            <property name="address" value="address ABC" />  
            <property name="age" value="29" />  
        </bean>  
        
    </beans>  

2. simple dependency checking

    <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-2.5.xsd">  
        
        <bean id="CustomerBean" class="com.mkyong.common.Customer"  
             dependency-check="simple">  
        
            <property name="person" ref="PersonBean" />  
            <property name="action" value="buy" />  
        </bean>  
        
        <bean id="PersonBean" class="com.mkyong.common.Person">  
            <property name="name" value="mkyong" />  
            <property name="address" value="address ABC" />  
            <property name="age" value="29" />  
        </bean>  
        
    </beans>  

注意此处type字段故意没有设置，这样会出现UnsatisfiedDependencyException

org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'CustomerBean' 
defined in class path resource [config/Spring-Customer.xml]: 
Unsatisfied dependency expressed through bean property 'type': 
Set this property value or disable dependency checking for this bean.

3. objects dependency checking

<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-2.5.xsd">  
    
    <bean id="CustomerBean" class="com.mkyong.common.Customer"  
         dependency-check="objects">  
    
        <property name="action" value="buy" />  
        <property name="type" value="1" />  
    </bean>  
    
    <bean id="PersonBean" class="com.mkyong.common.Person">  
        <property name="name" value="mkyong" />  
        <property name="address" value="address ABC" />  
        <property name="age" value="29" />  
    </bean>  
    
</beans> 

此处故意没有设置”person“属性，会出现UnsatisfiedDependencyException

org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'CustomerBean' 
defined in class path resource [config/Spring-Customer.xml]: 
Unsatisfied dependency expressed through bean property 'person': 
Set this property value or disable dependency checking for this bean.

4. all dependency checking

    <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-2.5.xsd">  
        
        <bean id="CustomerBean" class="com.mkyong.common.Customer"  
             dependency-check="all">  
        
            <property name="action" value="buy" />  
        </bean>  
        
        <bean id="PersonBean" class="com.mkyong.common.Person">  
            <property name="name" value="mkyong" />  
            <property name="address" value="address ABC" />  
            <property name="age" value="29" />  
        </bean>  
        
    </beans>  

Global default dependency checking：

default-dependency-check="all"

    <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-2.5.xsd"  
        default-dependency-check="all">  
        
        <bean id="CustomerBean" class="com.mkyong.common.Customer">  
            <property name="action" value="buy" />  
            <property name="type" value="1" />  
        </bean>  
        
        <bean id="PersonBean" class="com.mkyong.common.Person">  
            <property name="name" value="mkyong" />  
            <property name="address" value="address ABC" />  
            <property name="age" value="29" />  
        </bean>  
        
    </beans>