【Spring二】依赖注入(DI)及继承机制

发布时间：2020-12-13 22:17:34 所属栏目：百科来源：网络整理

导读：DI:dependency input? 所谓的依赖注入，就指给对象的属性赋值，有两种方式可以实现： public class Person{ private Long pid; private String pname; private Student student; private Set sets; private List lists; private Map map; private Properties

DI:dependency input?

所谓的依赖注入，就指给对象的属性赋值，有两种方式可以实现：

public class Person{
private Long pid;
private String pname;
private Student student;
private Set sets;
private List lists;
private Map map;
private Properties properties;

// set get方法

}

一.使用构造器进行注入：constructor-arg

1.在Person类中增加相应的构造方法：

public Person(String pname,Student student){

this.pname= pname;

this.student= student;

}

2.在配置文件中配置：

< bean id="student_con"class="cn.itheima03.spring.di.constructor.Student"></bean>

<beanid="person_con"class="cn.itheima03.spring.di.constructor.Person">

<!--

构造器的参数

index

参数的位置,从0开始计算

type

参数的类型

value

给基本属性赋值

ref

给引用类型赋值

-->

<constructor-argindex="0"value="王二麻子"></constructor-arg>

<constructor-argindex="1"ref="student_con"></constructor-arg>

</bean>

3.测试

ApplicationContext context = newClassPathXmlApplicationContext("applicationContext.xml");

Person person = (Person)context.getBean( "person_con" );

二.利用set方法进行注入：

配置文件中配置property属性：

< bean id="student"class="cn.itheima03.spring.di.Student"></bean>

< bean id="person"class="cn.itheima03.spring.di.Person">

<propertyname="pid"value="1"></property>

<propertyname="pname"value="王二麻子"></property>

<propertyname="student">

<refbean="student"/>

</property>

<propertyname="sets">

<set>

<refbean="student"/>

</set>

</property>

<propertyname="lists">

<list>

<refbean="student"/>

</list>

</property>

<propertyname="map">

<map>

<entrykey="key1">

</entry>

<entrykey="key2">

<refbean="student"/>

</entry>

</map>

</property>

<propertyname="properties">

<props>

<propkey="prop1">

prop1

</prop>

</props>

</property>

</ bean >

三.使用IOC和DI的例子：

1.Document接口即各个实现类：

Document.java:

public interfaceDocument {

public voidread();

public voidwrite();

}

WrodDocument.java:

public classWordDocumentimplementsDocument{

public voidread() {

System. out.println("read word");

}

public voidwrite() {

System. out.println("write word");

}

ExcelDocument.java:

public classExcelDocumentimplementsDocument{

public voidread() {

System. out.println("read excel");

}

public voidwrite() {

System. out.println("write excel");

}

DocumentManager.java:

public classDocumentManager {

private Documentdocument;

public DocumentManager(Document document){

this.document= document;

}

public DocumentManager){}

public voidsetDocument(Document document){

this.document= document;

}

public voidread(){

this.document.read();

}

public voidwrite(){

this.document.write();

}

2.配置文件：

< bean id="documentManager"class="com.oterman.practice.DocumentManager">

<propertyname="document"ref="wordDocment"></property>

</ bean >

< bean id="wordDocment"class="com.oterman.practice.WordDocument"></bean>

< bean id="excelDocument"class="com.oterman.practice.ExcelDocument"></bean>

3.测试：

/**

* 传统方式

@Test

public voidtest(){

Document document= newWordDocument();

DocumentManager dm= newDocumentManager(document);

dm.read();

}

/**

* 使用spring来完成，真正做到了面向接口编程。

@Test

public voidtest_spring(){

ApplicationContext context= newClassPathXmlApplicationContext("applicationContext.xml");

DocumentManager documentManager=(DocumentManager) context.getBean( "documentManager" );

documentManager.read();

}

四.继承机制

spring容器的继承机制：
两个属性:parent,指明父类
abstract,表示不为该类创建对象。

上述的parent：让student_extends拥有person_extends的属性的值 abstract:不让person_extends创建对象

（编辑：李大同）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!