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Spring IoC依赖注入的三种方式
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Spring容器在初始化过程中加载配置文件：

ClassPathXmlApplicationContext context =
    new ClassPathXmlApplicationContext("applicationContext.xml");

从中读取类路径和属性信息：

...
<bean id="sc" class="cn.tedu.springioc.beans.Student" autowire="byName">
    <property name="number" value="1001" />
    <property name="name" value="张飞" />
    <property name="gender" value="男" />
    <property name="age" value="20" />
    <property name="enrollment" ref="enrollment" />
</bean>
...

再通过反射创建该类的对象。

public class ObjectTest {
    public static void main(String[] args) {
        String classPath = "cn.tedu.springioc.beans.Student";

        try {
            Class<?> cls = Class.forName(classPath);
            Object obj = cls.getDeclaredConstructor().newInstance();

            Field[] fields = cls.getDeclaredFields();
            for (Field field : fields) {
                String fieldName = field.getName();
                String setMethodName = "set" +
                    fieldName.substring(0, 1).toUpperCase() +
                    fieldName.substring(1);
                Method setMethod = cls.getDeclaredMethod(
                    setMethodName, field.getType());

                if (fieldName.equals("number"))
                    setMethod.invoke(obj, "1001");
                else if (fieldName.equals("name"))
                    setMethod.invoke(obj, "张飞");
                else if (fieldName.equals("gender"))
                    setMethod.invoke(obj, "男");
                else if (fieldName.equals("age"))
                    setMethod.invoke(obj, 20);
                else if (fieldName.equals("enrollment"))
                    ;
                else if (fieldName.equals("subject"))
                    ;
            }

            System.out.println(obj);
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}

运行测试：

Student{number='1001', name='张飞', gender='男', age=20, enrollment=null, subject=null}

- 上面代码所采用的依赖(属性)注入(赋值)方式称为set方法注入，最常用
- 除Set方法注入以外，Spring还支持构造器注入和接口注入，后者不常用

例程：SpringIoC