目錄
1. 背景概念
1.1 DI定義
1.2 常見注入方式的xml配置
2. 簡單的StudentDI工程,展示了常見的注入方式的使用(配置)
2.1 maven系統的配置檔案:pom.xml
2.2 bean的配置檔案: bean_di.xml
2.3 類代碼:StudentDI.java , Address.java (該類被StudentDI引用)
2.4 測試類
補充:Eclipse中,一個快速生成getter和setter方法的小技巧
1. 背景概念
1.1 DI定義
(1) IoC的一個重點是:在系統運作中,動态的向某個對象提供它所需要的其他對象。這一點是通過DI來實作的。
(2)DI, 依賴注入:用一個單獨的對象(裝配器)來裝配對象之間的依賴關系。DI,即元件之間的依賴關系由容器在運作期間決定,即由容器動态的将某個依賴關系注入到元件中。
(3)舉例:
對象A要操作資料庫,以前我們要在A中自己編寫代碼來獲得一個Connection對象,有了Spring後我們就隻需要告訴Spring, A中需要一個Connection. 至于怎麼構造這個connection?何時構造?A不需要知道。這樣就完成了對各個對象之間關系的控制。
(4)DI如何實作?通過反射。它允許程式在運作的時候動态的生成對象,執行對象的方法,改變對象的屬性,Spring就是通過反射來實作注入的。
1.2 常見注入方式的xml配置
bean注入
數組注入
List注入
Map注入
set注入
null注入
Properties注入
2. 簡單的StudentDI工程,展示了常見的注入方式的使用(配置)
2.1 maven系統的配置檔案:pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.my.test</groupId>
<artifactId>SpringDIDemo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.3.3</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>1.9.4</version>
</dependency>
</dependencies>
</project>
2.2 bean的配置檔案: bean_di.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"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:c="http://www.springframework.org/schema/c"
xsi:schemaLocation="http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
https://www.springframework.org/schema/context/spring-context.xsd">
<context:annotation-config />
<bean id="addr" class="com.my.test.Address">
<property name="address" value="上海" />
</bean>
<bean id="student1" class="com.my.test.StudentDI">
<property name="name" value="Sheryl" />
<property name="address" ref="addr" />
<property name="books">
<array>
<value>數學</value>
<value>國文</value>
<value>英語</value>
</array>
</property>
<property name="hobbys">
<list>
<value>聽歌</value>
<value>看電影</value>
<value>逛街</value>
</list>
</property>
<property name="card">
<map>
<entry key="招行" value="123456789" />
<entry key="工行" value="987654321" />
</map>
</property>
<property name="games">
<set>
<value>CS</value>
<value>鬥地主</value>
<value>高爾夫</value>
</set>
</property>
<property name="wife">
<null />
</property>
<property name="info">
<props>
<prop key="學号">12345678</prop>
<prop key="性别">女</prop>
<prop key="姓名">Sheryl</prop>
</props>
</property>
</bean>
</beans>
2.3 類代碼:StudentDI.java , Address.java (該類被StudentDI引用)
(1)StudentDI.java
package com.my.test;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import com.my.test.Address;
public class StudentDI {
private String name;
private Address address;
private String[] books;
private List<String> hobbys;
private Map<String,String> card;
private Set<String> games;
private String wife;
private Properties info;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
public String[] getBooks() {
return books;
}
public void setBooks(String[] books) {
this.books = books;
}
public List<String> getHobbys() {
return hobbys;
}
public void setHobbys(List<String> hobbys) {
this.hobbys = hobbys;
}
public Map<String, String> getCard() {
return card;
}
public void setCard(Map<String, String> card) {
this.card = card;
}
public Set<String> getGames() {
return games;
}
public void setGames(Set<String> games) {
this.games = games;
}
public String getWife() {
return wife;
}
public void setWife(String wife) {
this.wife = wife;
}
public Properties getInfo() {
return info;
}
public void setInfo(Properties info) {
this.info = info;
}
public void showStudentInfo(){
System.out.println("name="+ name+ ",address="+ address.getAddress()+ ",books=");
for (String book:books){
System.out.print("<<"+book+">>\t");
}
System.out.println("\nhobbys:"+hobbys);
System.out.println("card:"+card);
System.out.println("games:"+games);
System.out.println("wife:"+wife);
System.out.println("info:"+info);
}
}
(2)Address.java
package com.my.test;
public class Address {
private String address;
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
2.4 測試類
package com.my.test.demo;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.my.test.StudentDI;
public class StudentDITest {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("bean_di.xml");
StudentDI studentDI = (StudentDI) context.getBean("student1");
studentDI.showStudentInfo();
}
}
輸出結果:
name=Sheryl,address=上海,books=
<<數學>> <<國文>> <<英語>>
hobbys:[聽歌, 看電影, 逛街]
card:{招行=123456789, 工行=987654321}
games:[CS, 鬥地主, 高爾夫]
wife:null
info:{學号=12345678, 性别=女, 姓名=Sheryl}