Spring中bean实例化的三种方式：默认构造、静态工厂、实例工厂

1. 默认构造方式：必须提供默认构造

<bean id="bean id" class="工厂全限定类名"></bean>

以Studnet类为例

public class Student {
	
	private int id;
	private String name;
	private int age;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public String toString() {
		return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
	}
		
}

applicationContext.xml配置

<bean id="Student" class="com.wuwl.entity.Student">
	<property name="id" value="520"></property>
	<property name="name" value="tom"></property>
	<property name="age" value="13"></property>
</bean>

测试方法

	public static void testStudent() {
		 ApplicationContext ac =new ClassPathXmlApplicationContext("applicationContext.xml");
		 Student student = ac.getBean("Student", Student.class);
		 System.out.println(student);
	}

2. 静态工厂：常用于spring整合其他框架(工具)，所有方法必须是static

<bean id="bean id" class="工厂全限定类名"  factory-method="静态方法"></bean>

applicationContext.xml配置

<bean id="Student2" class="com.wuwl.entity.StudentStaticFactory" factory-method="getStudent">
	<!--**如果在此处不加上属性或对象，所有属性均为默认值，及时在对应的Student的bean中已经配置过了**-->
	<property name="id" value="520"></property>
	<property name="name" value="tom"></property>
	<property name="age" value="13"></property>
</bean>

测试方法

	public static void testStudentStaticFactory() {
		 ApplicationContext ac =new ClassPathXmlApplicationContext("applicationContext.xml");
		 Student student = ac.getBean("Student2", Student.class);
		 System.out.println(student);

	}

3. 实例工厂:必须现有工厂实例对象，再通过实例对象创建对象，提供所有的方法都必须是非静态方法

applicationContext.xml配置

<!--创建工厂实例-->
<bean id="StudentFactory" class="com.wuwl.entity.StudentFactory"></bean>
<!--创建对象-->
<bean id="Student1" factory-bean="StudentFactory" factory-method="getStudent">
	<!--**如果在此处不加上属性或对象，所有属性均为默认值，及时在对应的Student的bean中已经配置过了**-->
	<property name="id" value="520"></property>
	<property name="name" value="tom"></property>
	<property name="age" value="13"></property>
	</bean>

测试方法

public static void testStudentFactory() {
		 ApplicationContext ac =new ClassPathXmlApplicationContext("applicationContext.xml");
		 Student student = ac.getBean("Student1", Student.class);
		 System.out.println(student);
	}