spring注入方式详解

spring注入方式详解 (2010-01-10 19:10)

分类： java

一、使用setter方式完成依赖注入

下面是Bean和beans-config.xml文件。

public class HelloBean {

private String helloWord;



//...省略getter、setter方法

}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN"
"http://www./dtd/spring-beans.dtd">
<beans>
<bean id="helloBean"
class="onlyfun.caterpillar.HelloBean">
<property name="helloWord">
<value>Hello!Justin!</value>
</property>
</bean>
</beans>

public class SpringDemo {
public static void main(String[] args) {
Resource rs = new FileSystemResource("beans-config.xml");
BeanFactory factory = new XmlBeanFactory(rs);

HelloBean hello = (HelloBean) factory.getBean("helloBean");
System.out.println(hello.getHelloWord());
}
}

二、使用constructor方式完成注入

public class HelloBean {
private String name;
private String helloWord;

// 建议有要无参数建构方法
public HelloBean() {
}

public HelloBean(String name, String helloWord) {
this.name = name;
this.helloWord = helloWord;
}

//...省略getter、setter方法
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN"
"http://www./dtd/spring-beans.dtd">
<beans>
<bean id="helloBean"
class="onlyfun.caterpillar.HelloBean">
<constructor-arg index="0">
<value>Justin</value>
</constructor-arg>
<constructor-arg index="1">
<value>Hello</value>
</constructor-arg>
</bean>
</beans>

public class SpringDemo {
public static void main(String[] args) {
ApplicationContext context =
new FileSystemXmlApplicationContext("beans-config.xml");

HelloBean hello = (HelloBean) context.getBean("helloBean");
System.out.print("Name: ");
System.out.println(hello.getName());
System.out.print("Word: ");
System.out.println(hello.getHelloWord());
}
}

三、属性参考

public class HelloBean {
private String helloWord;
private Date date;

//...省略getter、setter方法
}

<beans>
<bean id="dateBean" class="java.util.Date"/>
<bean id="helloBean" class="onlyfun.caterpillar.HelloBean">
<property name="helloWord">
<value>Hello!</value>
</property>
<property name="date">
<ref bean="dateBean"/>
</property>
</bean>
</beans>

public class SpringDemo {
public static void main(String[] args) {
ApplicationContext context =
new FileSystemXmlApplicationContext("beans-config.xml");

HelloBean hello = (HelloBean) context.getBean("helloBean");
System.out.print(hello.getHelloWord());
System.out.print(" It's ");
System.out.print(hello.getDate());
System.out.println(".");
}
}

四、“byType”自动绑定

将“三”中的配置文件改为下面，即可完成bean属性的按类型自动绑定。

<beans>
<bean id="dateBean" class="java.util.Date"/>
<bean id="helloBean" class="onlyfun.caterpillar.HelloBean" autowire="byType">
<property name="helloWord">
<value>Hello!</value>
</property>
</bean>
</beans>

五、“byName”自动绑定

将“三”中的配置文件改为下面，即可完成bean属性的按名称自动绑定。

<beans>
<bean id="dateBean" class="java.util.Date"/>
<bean id="helloBean" class="onlyfun.caterpillar.HelloBean" autowire="byName">
<property name="helloWord">
<value>Hello!</value>
</property>
</bean>
</beans>

六、“constructor”自动绑定

将“三”中的配置文件改为下面，即可完成bean属性的按构造方法自动绑定。在建立依赖关系时，Srping容器会试图比对容器中的Bean实例类型，及相关的构造方法上的参数类型，看看在类型上是否符合，如果有的话，则选用该构造方法来建立Bean实例。如果无法绑定，则抛出org.springframework.beans.factory.UnsatisfiedDependencyException异常。

<beans>
<bean id="dateBean" class="java.util.Date"/>
<bean id="helloBean" class="onlyfun.caterpillar.HelloBean" autowire="constructor">
<property name="helloWord">
<value>Hello!</value>
</property>
</bean>
</beans>

六、“autodetect”自动绑定

将“三”中的配置文件改为下面，即可完成bean属性的自动绑定，这个自动绑定是Spring会尝试用入constructor来处理依赖关系的建立，如果不行，则再尝试用byType类建立依赖关系。

<beans>
<bean id="dateBean" class="java.util.Date"/>
<bean id="helloBean" class="onlyfun.caterpillar.HelloBean" autowire="autodetect">
<property name="helloWord">
<value>Hello!</value>
</property>
</bean>
</beans>

七、依赖检查方式

在自动绑定中，由于没办法从定义文件中，清楚地看到是否每个属性都完成设定，为了确定某些依赖关系确实建立，您可以假如依赖检查，在<bean>标签使用时设定"dependency-check"，可以有四种依赖检查方式：simple、objects、all、none。

simple：只检查简单的类型（像原生数据类型或字符串对象）属性是否完成依赖关系，。

objects：检查对象类型的属性是否完成依赖关系。

all：则检查全部的属性是否完成依赖关系。

none：设定是默认值，表示不检查依赖性。

<beans>
<bean id="dateBean" class="java.util.Date"/>
<bean id="helloBean" class="onlyfun.caterpillar.HelloBean" autowire="autodetect" dependeny-check="all">
<property name="helloWord">
<value>Hello!</value>
</property>
</bean>
</beans>

八、集合对象注入

对于像数组、List、Set、Map等集合对象，在注入前必须填充一些对象至集合中，然后再将集合对象注入至所需的Bean时，也可以交由Spring的IoC容器来自动维护或生成集合对象，并完成依赖注入。

public class SomeBean {
private String[] someStrArray;
private Some[] someObjArray;
private List someList;
private Map someMap;

public String[] getSomeStrArray() {
return someStrArray;
}
public void setSomeStrArray(String[] someStrArray) {
this.someStrArray = someStrArray;
}
public Some[] getSomeObjArray() {
return someObjArray;
}
public void setSomeObjArray(Some[] someObjArray) {
this.someObjArray = someObjArray;
}
public List getSomeList() {
return someList;
}
public void setSomeList(List someList) {
this.someList = someList;
}
public Map getSomeMap() {
return someMap;
}
public void setSomeMap(Map someMap) {
this.someMap = someMap;
}
}

public class Some {
private String name;

public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String toString() {
return name;
}
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN"
"http://www./dtd/spring-beans.dtd">

<beans>
<bean id="some1" class="onlyfun.caterpillar.Some">
<property name="name">
<value>Justin</value>
</property>
</bean>

<bean id="some2" class="onlyfun.caterpillar.Some">
<property name="name">
<value>momor</value>
</property>
</bean>

<bean id="someBean" class="onlyfun.caterpillar.SomeBean">
<property name="someStrArray">
<list>
<value>Hello</value>
<value>Welcome</value>
</list>
</property>

<property name="someObjArray">
<list>
<ref bean="some1"/>
<ref bean="some2"/>
</list>
</property>

<property name="someList">
<list>
<value>ListTest</value>
<ref bean="some1"/>
<ref bean="some2"/>
</list>
</property>

<property name="someMap">
<map>
<entry key="MapTest">
<value>Hello!Justin!</value>
</entry>
<entry key="someKey1">
<ref bean="some1"/>
</entry>
</map>
</property>
</bean>
</beans>

public class SpringDemo {
public static void main(String[] args) {
ApplicationContext context =
new FileSystemXmlApplicationContext(
"beans-config.xml");

SomeBean someBean =
(SomeBean) context.getBean("someBean");

// 取得数组型态依赖注入对象
String[] strs =
(String[]) someBean.getSomeStrArray();
Some[] somes =
(Some[]) someBean.getSomeObjArray();
for(int i = 0; i < strs.length; i++) {
System.out.println(strs[i] + ","
+ somes[i].getName());
}

// 取得List型态依赖注入对象
System.out.println();
List someList = (List) someBean.getSomeList();
for(int i = 0; i < someList.size(); i++) {
System.out.println(someList.get(i));
}

// 取得Map型态依赖注入对象
System.out.println();
Map someMap = (Map) someBean.getSomeMap();
System.out.println(someMap.get("MapTest"));
System.out.println(someMap.get("someKey1"));
}
}