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>