spring源码分析之FactoryBean

上文中描述spring加载bean的过程中，有一段关于FactoryBean的处理。所以今天讲一下FactoryBean。从名字上直译就是bean工厂,用来创建bean的。从Spring 3.0 开始， FactoryBean开始支持泛型，即接口声明改为FactoryBean 的形式：

package org.Springframework.beans.factory;
public interface FactoryBean<T> {

/**
* 返回由FactoryBean创建的bean实例，如果isSingleton()返回true，则该实          例会放到Spring容器中单实例缓存池中。
*/
T getObject() throws Exception;
/**
*返回FactoryBean创建的bean类型。
*/
Class<?> getObjectType();

/**
*返回由FactoryBean创建的bean实例的作用域是singleton还是prototype。
*/
boolean isSingleton();
}

下面就开始写今天要演示的2个例子

import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.commons.lang.builder.ToStringStyle;

public class Student {
private String name;
private String classname;
private String age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getClassname() {
return classname;
}
public void setClassname(String classname) {
this.classname = classname;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}

@Override
public String toString(){
return ToStringBuilder.reflectionToString(this,ToStringStyle.MULTI_LINE_STYLE);
}
}

import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.commons.lang.builder.ToStringStyle;
import org.springframework.beans.factory.FactoryBean;

public class StudentFactoryBean implements FactoryBean<Student> {

private String studentInfo;

@Override
public Student getObject() throws Exception {
Student s=new Student();
String[] studentInfos=studentInfo.split(",");
s.setName(studentInfos[0]);
s.setClassname(studentInfos[1]);
s.setAge(studentInfos[2]);
return s;
}

@Override
public Class<Student> getObjectType() {
return Student.class;
}

@Override
public boolean isSingleton() {
return false;
}

public String getStudentInfo() {
return studentInfo;
}

public void setStudentInfo(String studentInfo) {
this.studentInfo = studentInfo;
}
@Override
public String toString(){
return ToStringBuilder.reflectionToString(this,ToStringStyle.MULTI_LINE_STYLE);
}
}

bean id="studentFactoryBean" class="com.eroadsf.springdemo.factorybean.StudentFactoryBean">
<property name="studentInfo" value="测试1,JAVA班,18"></property>
</bean>

public class Test {
@SuppressWarnings("deprecation")
public static void main(String[] args) {
XmlBeanFactory f=new XmlBeanFactory(new ClassPathResource("spring-context.xml"));
Student s=(Student) f.getBean("studentFactoryBean");
System.out.println("获取student:\n"+s);
StudentFactoryBean sf=(StudentFactoryBean) f.getBean("&studentFactoryBean");//spring就是用&这个来判断获取的是bean还是FactoryBean
System.out.println("获取StudentFactoryBean:\n"+sf);

}

}

结果

获取student:

com.eroadsf.springdemo.factorybean.Student@9d63e96[

name=测试1

classname=JAVA班

age=18

]

获取StudentFactoryBean:

com.eroadsf.springdemo.factorybean.StudentFactoryBean@4d50a1ac[

studentInfo=测试1,JAVA班,18

]