Spring(五)之Bean定义继承和依赖注入
本文内容纲要：Spring(五)之Bean定义继承和依赖注入
一、Bean定义继承
bean定义可以包含许多配置信息，包括构造函数参数，属性值和特定于容器的信息，例如初始化方法，静态工厂方法名称等。
子bean定义从父定义继承配置数据。子定义可以根据需要覆盖某些值或添加其他值。
Spring Bean定义继承与Java类继承无关，但继承概念是相同的。您可以将父bean定义定义为模板，其他子bean可以从父bean继承所需的配置。
使用基于XML的配置元数据时，可以使用parent属性指定子bean定义，并将父bean指定为此属性的值。
演示示例:
(1)编写HelloWorld.java
package com.tutorialspoint;public class HelloWorld {
private String message1;
private String message2;
public void setMessage1(String message){
this.message1 = message;
}
public void setMessage2(String message){
this.message2 = message;
}
public void getMessage1(){
System.out.println("World Message1 : " + message1);
}
public void getMessage2(){
System.out.println("World Message2 : " + message2);
}
}
(2)编写HelloIndea.java
package com.tutorialspoint;public class HelloIndia {
private String message1;
private String message2;
private String message3;
public void setMessage1(String message){
this.message1 = message;
}
public void setMessage2(String message){
this.message2 = message;
}
public void setMessage3(String message){
this.message3 = message;
}
public void getMessage1(){
System.out.println("India Message1 : " + message1);
}
public void getMessage2(){
System.out.println("India Message2 : " + message2);
}
public void getMessage3(){
System.out.println("India Message3 : " + message3);
}
}
(3)编写MainApp.java
package com.tutorialspoint;import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
HelloWorld objA = (HelloWorld) context.getBean("helloWorld");
objA.getMessage1();
objA.getMessage2();
HelloIndia objB = (HelloIndia) context.getBean("helloIndia");
objB.getMessage1();
objB.getMessage2();
objB.getMessage3();
}
}
(4)Beans.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-4.0.xsd">
<bean id = "helloWorld" class = "com.tutorialspoint.HelloWorld">
<property name = "message1" value = "Hello World!"/>
<property name = "message2" value = "Hello Second World!"/>
</bean>
<bean id ="helloIndia" class = "com.tutorialspoint.HelloIndia" parent = "helloWorld">
<property name = "message1" value = "Hello India!"/>
<property name = "message3" value = "Namaste India!"/>
</bean>
</beans>
(5)运行MainApp.java中的main方法
二、依赖注入
每个基于Java的应用程序都有一些对象可以协同工作，以呈现最终用户所看到的工作应用程序。在编写复杂的Java应用程序时，应用程序类应尽可能独立于其他Java类，以增加重用这些类的可能性，并在单元测试时独立于其他类测试它们。依赖注入（或称为布线）有助于将这些类粘合在一起，同时保持它们的独立性。
依赖注入常用两种形式:
1.set注入（比较常用）
2.构造函数注入
set注入示例：
(1)编写TextEditor.java
package com.tutorialspoint;public class TextEditor {
private SpellChecker spellChecker;
// a setter method to inject the dependency.
public void setSpellChecker(SpellChecker spellChecker) {
System.out.println("Inside setSpellChecker." );
this.spellChecker = spellChecker;
}
// a getter method to return spellChecker
public SpellChecker getSpellChecker() {
return spellChecker;
}
public void spellCheck() {
spellChecker.checkSpelling();
}
}
(2)编写SpellChecker.java
package com.tutorialspoint;public class SpellChecker {
public SpellChecker(){
System.out.println("Inside SpellChecker constructor." );
}
public void checkSpelling(){
System.out.println("Inside checkSpelling." );
}
}
(3)编写Beans.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-4.0.xsd">
<!-- Definition for textEditor bean using inner bean -->
<bean id = "textEditor" class = "com.tutorialspoint.TextEditor">
<property name = "spellChecker">
<bean id = "spellChecker" class = "com.tutorialspoint.SpellChecker"/>
</property>
</bean>
</beans>
(4)编写MainApp.java
package com.tutorialspoint;import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
TextEditor te = (TextEditor) context.getBean("textEditor");
te.spellCheck();
}
}
(5)运行MainApp.java中的main方法
2.注入集合
Spring提供四种集合注入方式:
(1)Set;(2)List;(3)Map;(4)Props;
演示示例如下:
(1)编写JavaCollection
package com.tutorialspoint;import java.util.*;
public class JavaCollection {
List addressList;
Set addressSet;
Map addressMap;
Properties addressProp;
// a setter method to set List
public void setAddressList(List addressList) {
this.addressList = addressList;
}
// prints and returns all the elements of the list.
public List getAddressList() {
System.out.println("List Elements :" + addressList);
return addressList;
}
// a setter method to set Set
public void setAddressSet(Set addressSet) {
this.addressSet = addressSet;
}
// prints and returns all the elements of the Set.
public Set getAddressSet() {
System.out.println("Set Elements :" + addressSet);
return addressSet;
}
// a setter method to set Map
public void setAddressMap(Map addressMap) {
this.addressMap = addressMap;
}
// prints and returns all the elements of the Map.
public Map getAddressMap() {
System.out.println("Map Elements :" + addressMap);
return addressMap;
}
// a setter method to set Property
public void setAddressProp(Properties addressProp) {
this.addressProp = addressProp;
}
// prints and returns all the elements of the Property.
public Properties getAddressProp() {
System.out.println("Property Elements :" + addressProp);
return addressProp;
}
}
(2)编写Beans.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-4.0.xsd">
<!-- Definition for javaCollection -->
<bean id = "javaCollection" class = "com.tutorialspoint.JavaCollection">
<!-- results in a setAddressList(java.util.List) call -->
<property name = "addressList">
<list>
<value>INDIA</value>
<value>Pakistan</value>
<value>USA</value>
<value>USA</value>
</list>
</property>
<!-- results in a setAddressSet(java.util.Set) call -->
<property name = "addressSet">
<set>
<value>INDIA</value>
<value>Pakistan</value>
<value>USA</value>
<value>USA</value>
</set>
</property>
<!-- results in a setAddressMap(java.util.Map) call -->
<property name = "addressMap">
<map>
<entry key = "1" value = "INDIA"/>
<entry key = "2" value = "Pakistan"/>
<entry key = "3" value = "USA"/>
<entry key = "4" value = "USA"/>
</map>
</property>
<!-- results in a setAddressProp(java.util.Properties) call -->
<property name = "addressProp">
<props>
<prop key = "one">INDIA</prop>
<prop key = "one">INDIA</prop>
<prop key = "two">Pakistan</prop>
<prop key = "three">USA</prop>
<prop key = "four">USA</prop>
</props>
</property>
</bean>
</beans>
(3)编写MainApp.java
package com.tutorialspoint;import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
JavaCollection jc=(JavaCollection)context.getBean("javaCollection");
jc.getAddressList();
jc.getAddressSet();
jc.getAddressMap();
jc.getAddressProp();
}
}
(4)运行MainApp.java中的main方法
结果如下:
本文内容总结：Spring(五)之Bean定义继承和依赖注入
原文链接：https://www.cnblogs.com/youcong/p/9459946.html
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