Spring Bean基本管理

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.springframework.org/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.springframework.org/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.springframework.org/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")); 
    }  
}