Java Qiao Xiaosong-injection of spring constructor and null Injection

Spring constructor Injection

Spring's most primitive constructor injection method is:

 

<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>

The following describes the injection methods of common spring constructor functions.

 

 

1. Based on the type of the constructor Parameter

 

<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. index-based injection

 

 

 

<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. Inject according to the parameter name

 

 

 

<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>

 

 

The following are the two classes I have defined:

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;}@Overridepublic 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;}@Overridepublic 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 =" Ministry of Education "/> </bean> </beans>

 

 

Injection of null values in spring

 

 

<? 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 is a string --> <property name = "name"> <null/> </property> <property name = "Dept"> <null/> </property> </bean> </beans>