spring框架学习（二）依赖注入

转自：http://blog.csdn.net/lishuangzhe7047/article/details/20740835

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spring框架为我们提供了三种注入方式，分别是set注入，构造方法注入，接口注入。接口注入不作要求，下面介绍前两种方式。

1，set注入

采用属性的set方法进行初始化，就成为set注入。

1）给普通字符类型赋值。

[java] view plain copy print ?

public class User{
privateString username;
publicString getUsername() {
returnusername;
}
publicvoid setUsername(String username) {
this.username= username;
}
}

public class User{
   privateString username;
 
   publicString getUsername() {
       returnusername;
   }
   publicvoid setUsername(String username) {
      this.username= username;
   }
}

我们只需要提供属性的set方法，然后去属性文件中去配置好让框架能够找到applicationContext.xml文件的beans标签。标签beans中添加bean标签，指定id，class值，id值不做要求，class值为对象所在的完整路径。bean标签再添加property 标签，要求，name值与User类中对应的属性名称一致。value值就是我们要给User类中的username属性赋的值。

[html] view plain copy print ?

<bean id="userAction"class="com.lsz.spring.action.User" >
<SPAN style="WHITE-SPACE: pre"> </SPAN><property name="username" value="admin"></property>
</bean>

<bean id="userAction"class="com.lsz.spring.action.User" >
	<property name="username" value="admin"></property>
</bean>

2）给对象赋值

同样提供对象的set方法

[java] view plain copy print ?

public class User{
private UserService userservice;
public UserServicegetUserservice() {
returnuser;
}
public void setUserservice(UserService userservice){
this.userservice= userservice;
}
}

public class User{
     private UserService userservice;
     public UserServicegetUserservice() {
          returnuser;
     }
     public void setUserservice(UserService userservice){
         this.userservice= userservice;
     }
}

配置文件中要增加UserService的bean标签声明及User对象对UserService引用。

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<bean id="userService" class="com.lsz.spring.service.UserService"></bean>
<bean id="userAction"class="com.lsz.spring.action.User" >
<property name="userservice" ref="userService"></property>
</bean>

<!--对象的声明-->
<bean id="userService" class="com.lsz.spring.service.UserService"></bean>
 
<bean id="userAction"class="com.lsz.spring.action.User" >
   <property name="userservice" ref="userService"></property>
</bean>

这样配置，框架就会将UserService对象注入到User类中。

3）给list集合赋值

同样提供set方法

[java] view plain copy print ?

public class User{
privateList<String> username;
publicList<String> getUsername() {
returnusername;
}
publicvoid setUsername(List<String> username) {
this.username= username;
}
}

public class User{
    privateList<String> username;
    publicList<String> getUsername() {
        returnusername;
    }
    publicvoid setUsername(List<String> username) {
        this.username= username;
    }
}

[html] view plain copy print ?

<bean id="userAction"class="com.lsz.spring.action.User" >
<propertynamepropertyname="username">
<list>
<value>zhang,san</value>
<value>lisi</value>
<value>wangwu</value>
</list>
</property>
</bean>

<bean id="userAction"class="com.lsz.spring.action.User" >
     <propertyname="username">
           <list>
               <value>zhang,san</value>
               <value>lisi</value>
               <value>wangwu</value>                                
               </list>
    </property>
</bean>

4）给属性文件中的字段赋值

[java] view plain copy print ?

public class User{
privateProperties props ;
publicProperties getProps() {
returnprops;
}
publicvoid setProps(Properties props) {
this.props= props;
}
}

public class User{
    privateProperties props ;
    publicProperties getProps() {
        returnprops;
    }
    publicvoid setProps(Properties props) {
        this.props= props;
    }
}

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<bean>
<propertynamepropertyname="props">
<props>
<propkeypropkey="url">jdbc:oracle:thin:@localhost:orl</prop>
<propkeypropkey="driverName">oracle.jdbc.driver.OracleDriver</prop>
<propkeypropkey="username">scott</prop>
<propkeypropkey="password">tiger</prop>
</props>
</property>
</bean>

<bean>
    <propertyname="props">
        <props>
           <propkey="url">jdbc:oracle:thin:@localhost:orl</prop>
           <propkey="driverName">oracle.jdbc.driver.OracleDriver</prop>
           <propkey="username">scott</prop>
           <propkey="password">tiger</prop>
        </props>
    </property>
</bean>

<prop>标签中的key值是.properties属性文件中的名称

注意：

无论给什么赋值，配置文件中<property>标签的name属性值一定是和对象中名称一致。

2构造方法注入

1）构造方法一个参数

[java] view plain copy print ?

public class User{
privateString usercode;
publicUser(String usercode) {
this.usercode=usercode;
}
}

public class User{
    privateString usercode;
    publicUser(String usercode) {
        this.usercode=usercode;
    }
}

[html] view plain copy print ?

<bean id="userAction"class="com.lsz.spring.action.User">
<constructor-argvalueconstructor-argvalue="admin"></constructor-arg>
</bean>

<bean id="userAction"class="com.lsz.spring.action.User">                        
    <constructor-argvalue="admin"></constructor-arg>                        
</bean>

2）构造函数有两个参数时

当参数为非字符串类型时，在配置文件中需要制定类型，如果不指定类型一律按照字符串类型赋值。

当参数类型不一致时，框架是按照字符串的类型进行查找的，因此需要在配置文件中制定是参数的位置

[html] view plain copy print ?

<constructor-argvalueconstructor-argvalue="admin"index="0"></constructor-arg>
<constructor-argvalueconstructor-argvalue="23" type="int"index="1"></constructor-arg>

<constructor-argvalue="admin"index="0"></constructor-arg>                
<constructor-argvalue="23" type="int"index="1"></constructor-arg>

这样制定，就是构造函数中，第一个参数为string类型，第二个参数为int类型