Java乔晓松-spring构造函数的注入以及null的注入
spring构造函数的注入
spring最原始的构造函数的注入方式是：
<bean id="employee" class="www.csdn.spring.cust.Employee"> <constructor-arg value="qiao" /> <constructor-arg value="20" /> <constructor-arg ref="dept" /> <constructor-arg value="nv" /> </bean>
下面的是常用的spring构造函数的注入方式
1、根据构造器参数的类型
<bean id="employee" class="www.csdn.spring.cust.Employee"> <constructor-arg type="java.lang.String" value="qiao" /> <constructor-arg type="java.lang.Integer" value="20" /> <constructor-arg type="www.csdn.spring.cust.Dept" ref="dept" /> <constructor-arg type="java.lang.String" value="nv" /> </bean>
2、根据索引index注入
<bean id="employee" class="www.csdn.spring.cust.Employee"> <constructor-arg index="0" value="qiao" /> <constructor-arg index="1" value="20" /> <constructor-arg index="2" ref="dept" /> <constructor-arg index="3" value="nv" /> </bean>
3、根据参数的名称注入
<bean id="employee" class="www.csdn.spring.cust.Employee"> <constructor-arg name="name" value="qiao" /> <constructor-arg name="age" value="20" /> <constructor-arg name="dept" ref="dept" /> <constructor-arg name="sex" value="nv" /> </bean>
下面是我定义的2个类
Dept.java
package www.csdn.spring.cust;
public class Dept {
public String num;
public String name;
public void setNum(String num) {
this.num = num;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Dept [num=" + num + ", name=" + name + "]";
}
}
Employee.java
package www.csdn.spring.cust;
public class Employee {
public String name;
public Integer age;
public Dept dept;
public String sex;
public Employee(String name, Integer age, Dept dept, String sex) {
super();
this.name = name;
this.age = age;
this.dept = dept;
this.sex = sex;
}
@Override
public String toString() {
return "Member [name=" + name + ", age=" + age + ", dept=" + dept
+ ", sex=" + sex + "]";
}
}
spring.xml
<?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="employee" class="www.csdn.spring.cust.Employee"> <constructor-arg
value="qiao" /> <constructor-arg value="20" /> <constructor-arg ref="dept"
/> <constructor-arg value="nv" /> </bean> -->
<!-- <bean id="employee" class="www.csdn.spring.cust.Employee"> <constructor-arg
type="java.lang.String" value="qiao" /> <constructor-arg type="java.lang.Integer"
value="20" /> <constructor-arg type="www.csdn.spring.cust.Dept" ref="dept"
/> <constructor-arg type="java.lang.String" value="nv" /> </bean> -->
<!-- <bean id="employee" class="www.csdn.spring.cust.Employee"> <constructor-arg
index="0" value="qiao" /> <constructor-arg index="1" value="20" /> <constructor-arg
index="2" ref="dept" /> <constructor-arg index="3" value="nv" /> </bean> -->
<bean id="employee" class="www.csdn.spring.cust.Employee">
<constructor-arg name="name" value="qiao" />
<constructor-arg name="age" value="20" />
<constructor-arg name="dept" ref="dept" />
<constructor-arg name="sex" value="nv" />
</bean>
<bean id="dept" class="www.csdn.spring.cust.Dept">
<property name="num" value="xx001" />
<property name="name" value="教育部" />
</bean>
</beans>
spring中null值的注入
<?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="employee" class="www.csdn.spring.cust.Employee">
<!-- value="null" null是字符串 -->
<property name="name">
<null />
</property>
<property name="dept">
<null />
</property>
</bean>
</beans>