【Spring二】依赖注入(DI)及继承机制

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"> <!-- property用来描述属性 --> <!-- 基本属性 --> <propertyname="pid"value="1"></property> <propertyname="pname"value="王二麻子"></property> <!-- 引用属性 --> <propertyname="student"> <refbean="student"/> </property> <!--集合 --> <propertyname="sets"> <set> <value>set1</value> <value>set2</value> <refbean="student"/> </set> </property> <propertyname="lists"> <list> <value>list1</value> <value>list2</value> <refbean="student"/> </list> </property> <propertyname="map"> <map> <entrykey="key1"> <value>map1</value> </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"> <!-- <constructor-argindex="0"ref="excelDocument"></constructor-arg> --> <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。

<bean id="person_extends" class="cn.itheima03.spring.extend.Person" abstract="true"> <property name="s" value="aaaa"></property> </bean> <bean id="student_extends" class="cn.itheima03.spring.extend.Student" parent="person_extends"> </bean>

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