Bean实例在调用无参构造器创建了空值对象后，就要对Bean对象的属性进行初始化。初始化是由容器自动完成的，称为注入。常用方式分为设值注入和构造注入。

3.1 基于xml-设值注入

通过set方法注入，基本数据类型用value，引用数据类型用ref。

applicationContext.xml

<bean id="mySchool" class="com.bjpowernode.di01.School">
    <property name="name" value="清华大学" />
</bean>

<bean id="myStudent" class="com.bjpowernode.di01.Student">
    <property name="name" value="张三" />
    <property name="age" value="23"></property>
    <property name="school" ref="mySchool"></property>
</bean>

School.class

public class School {
    private String name;
    public void setName(String name) {
        this.name = name;
    }

}

Student.class

public class Student {

    private String name;
    private int age;
    private School school;

    public Student() {
        super();
    }

    public void setSchool(School school) {
        this.school = school;
    }

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

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Student [name=" + name + ", age=" + age + ", school=" + school + "]";
    }

}

3.2 基于xml-为集合属性赋值

Some.class

public class Some {
    private School[] schools;
    private String[] myStrs;
    private List<String> myList;
    private Set<String> mySet;
    private Map<String,Object> myMap;
    private Properties myPros;
    ...
    set 方法
    ...
    @Override
    public String toString() {
        return "Some [schools=" + Arrays.toString(schools) + ", mystrs=" + Arrays.toString(myStrs) + ", myList="
                + myList + ", mySet=" + mySet + ", myMap=" + myMap + ", myPros=" + myPros + "]";
    }
}

applicationContext.xml

<bean id="mySchool1" class="com.bjpowernode.di02.School">
    <property name="name" value="清华大学" />
</bean>

<bean id="mySchool2" class="com.bjpowernode.di02.School">
    <property name="name" value="北京大学" />
</bean>

<bean id="mySome" class="com.bjpowernode.di02.Some">
    <property name="schools">
        <array>
            <ref bean="mySchool1"/>
            <ref bean="mySchool2"/>
        </array>
    </property>

    <property name="myStrs">
        <array>
            <value>山东</value>
            <value>临沂</value>
        </array>
    </property>

    <property name="myList">
        <list>
            <value>平邑</value>
            <value>一村</value>
        </list>
    </property>

    <property name="mySet">
        <set>
            <value>一街道</value>
            <value>二街道</value>
        </set>
    </property>

    <property name="myMap">
        <map>
            <entry key="mobile" value="15011111111"></entry>
            <entry key="qq" value="11111"></entry>
        </map>
    </property>

    <property name="myPros">
        <props>
            <prop key="age">12</prop>
            <prop key="sex">femal</prop>
        </props>
    </property>
</bean>

3.3 基于xml-域属性-自动注入

3.3.1 基于xml-autowire="byName"

会从容器中查找与Student类中域属性名scholl相同的Bean的id，并将该Bean对象自动注入给该域属性

<bean id="school" class="com.bjpowernode.di01.School">
    <property name="name" value="清华大学" />
</bean>

<bean id="myStudent" class="com.bjpowernode.di01.Student" autowire="byName">
    <property name="name" value="张三" />
    <property name="age" value="23"></property>
</bean>

3.3.2 基于xml-autowire="byType"

会从容器中查找与Student类中域属性类型School具有is-a关系的Bean，并将该Bean对象自动注入给该域属性

<bean id="mySchool" class="com.bjpowernode.di01.School">
    <property name="name" value="清华大学" />
</bean>

<bean id="myStudent" class="com.bjpowernode.di01.Student" autowire="byType">
    <property name="name" value="张三" />
    <property name="age" value="23"></property>
</bean>

3.3.3 基于xml-DI-SPEL注入

<bean id="myPerson" class="com.bjpowernode.di01.Person">
    <property name="pname" value="lisi"></property>
    <!-- 通过spring el表达式调用静态方法 -->
    <property name="page" value="#{T(java.lang.Math).random() * 50}"></property>
</bean>

<bean id="myStudent" class="com.bjpowernode.di01.Student">
    <!-- 调用其它Bean的属性 -->
    <property name="name" value="#{myPerson.pname}"></property>
    <!-- 运算 -->
    <property name="age" value="#{myPerson.page > 25 ? 25 : myPerson.page}"></property>
    <!-- 调用其它Bean的成员方法 -->
    <property name="age" value="#{myPerson.computeAge()}"></property>
</bean>

3.4 为应用指定多个Spring配置文件

(1)、平等关系的配置文件

两个配置文件：

• com/bjpowernode/di01/spring-base.xml

• com/bjpowernode/di01/spring-beans.xml

创建容器：

String source01 = "com/bjpowernode/di01/spring-base.xml";
String source02 = "com/bjpowernode/di01/spring-beans.xml";
ApplicationContext ac = new ClassPathXmlApplicationContext(source01,source02);

通配符

String source = "com/bjpowernode/di01/spring-*.xml";
ApplicationContext ac = new ClassPathXmlApplicationContext(source);

(2)、包含关系的配置文件

三个配置文件：

• com/bjpowernode/di01/applicationContext.xml

• com/bjpowernode/di01/spring-base.xml

• com/bjpowernode/di01/spring-beans.xml

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
...
>
   <!--引入其它的配置文件-->     
    <import resource="classpath:com/bjpowernode/di01/spring-base.xml" />
    <import resource="classpath:com/bjpowernode/di01/spring-beans.xml" />

    <!--通配符-->
    <import resource="classpath:com/bjpowernode/di01/spring-*.xml" />