Spring Bean基本管理

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" ?>  
  "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" ?>  
  "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" ?>  
  "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"));
    }  
}

 

参考资料：

《Spring开发指南》