spring注入的几种方式

1、setter方式（最常用）

  就是在bean中的属性必须有setter方法 然后在xml在配置

2、构造方法（不常用）

参考官方api的例子：

 

<beans>
    <bean name="foo" class="x.y.Foo">
        <constructor-arg>
            <bean class="x.y.Bar"/><!--相当于new了一个Bar对象-->
        </constructor-arg>
        <constructor-arg>
            <bean class="x.y.Baz"/>
        </constructor-arg>
    </bean>
</beans>

 

 如果构造方法需要多个参数 则可以按照参数索引赋值或类型赋值（参数中没有相同类型 ）

a.按参数类型传给构造方法注入[ Constructor Argument Type Matching ]

 

<bean id="exampleBean" class="examples.ExampleBean">
  <constructor-arg type="int" value="7500000"/>
  <constructor-arg type="java.lang.String" value="42"/>
</bean>

  b.按参数索引传给构造方法注入（索引从0开始）[ Constructor Argument Index ]

 

 

<bean id="exampleBean" class="examples.ExampleBean">
  <constructor-arg index="0" value="7500000"/>
  <constructor-arg index="1" value="42"/>
</bean>

 

Some examples

 

<bean id="exampleBean" class="examples.ExampleBean">

  <!-- setter injection using the nested <ref/> element -->
  <property name="beanOne"><ref bean="anotherExampleBean"/></property>

  <!-- setter injection using the neater 'ref' attribute -->
  <property name="beanTwo" ref="yetAnotherBean"/>
  <property name="integerProperty" value="1"/>
</bean>

<bean id="anotherExampleBean" class="examples.AnotherBean"/>
<bean id="yetAnotherBean" class="examples.YetAnotherBean"/>

 

 

public class ExampleBean {

    private AnotherBean beanOne;
    private YetAnotherBean beanTwo;
    private int i;

    public void setBeanOne(AnotherBean beanOne) {
        this.beanOne = beanOne;
    }

    public void setBeanTwo(YetAnotherBean beanTwo) {
        this.beanTwo = beanTwo;
    }

    public void setIntegerProperty(int i) {
        this.i = i;
    }    
}

 

 

<bean id="exampleBean" class="examples.ExampleBean">

  <!-- constructor injection using the nested <ref/> element -->
  <constructor-arg>
    <ref bean="anotherExampleBean"/>
  </constructor-arg>
  
  <!-- constructor injection using the neater 'ref' attribute -->
  <constructor-arg ref="yetAnotherBean"/>
  
  <constructor-arg type="int" value="1"/>
</bean>

<bean id="anotherExampleBean" class="examples.AnotherBean"/>
<bean id="yetAnotherBean" class="examples.YetAnotherBean"/>

 

 

public class ExampleBean {

    private AnotherBean beanOne;
    private YetAnotherBean beanTwo;
    private int i;
    
    public ExampleBean(
        AnotherBean anotherBean, YetAnotherBean yetAnotherBean, int i) {
        this.beanOne = anotherBean;
        this.beanTwo = yetAnotherBean;
        this.i = i;
    }
}

 

 

<bean id="exampleBean" class="examples.ExampleBean"
      factory-method="createInstance">
  <constructor-arg ref="anotherExampleBean"/>
  <constructor-arg ref="yetAnotherBean"/>
  <constructor-arg value="1"/> 
</bean>

<bean id="anotherExampleBean" class="examples.AnotherBean"/>
<bean id="yetAnotherBean" class="examples.YetAnotherBean"/>

 

 

public class ExampleBean {

    // a private constructor
    private ExampleBean(...) {
      ...
    }
    
    // a static factory method; the arguments to this method can be
    // considered the dependencies of the bean that is returned,
    // regardless of how those arguments are actually used.
    public static ExampleBean createInstance (
            AnotherBean anotherBean, YetAnotherBean yetAnotherBean, int i) {

        ExampleBean eb = new ExampleBean (...);
        // some other operations...
        return eb;
    }
}

 

 

 

3、接口注入（不常用）

网上说会增加耦合 不建议使用 我也没有用过 暂且先不谈 会了的话在更新^_^