方法一：使用构造器实例化bean
java代码：
package com.model;
public class User {
private String username;
public User(){
}
public User(String username){
this.setUsername(username);
}
public void sayHello(){
System.out.println("hello ");
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
}
配置文件：
<!--方法一：使用构造器实例化bean -->
<bean id="user" class="com.model.User"></bean>
测试代码：
ApplicationContext applicationContext = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
//方法一：使用构造器实例化bean
User user = (User)applicationContext.getBean("user");
user.sayHello();
方法二：使用静态工厂方法实例化bean
java代码：
package com.test;
public class StaticFactory {
private static StaticFactory staticFactory = new StaticFactory();
public static StaticFactory getBean() {
return staticFactory;
}
public void say() {
System.out.println("new Instance!");
}
}
配置文件：
<!--方法二：使用静态工厂方法实例化bean -->
<bean id="staticFactory" class="com.test.StaticFactory" factory-method="getBean"/>
测试代码：
ApplicationContext applicationContext = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
//方法二：使用静态工厂方法实例化bean
StaticFactory staticFactory = (StaticFactory)applicationContext.getBean("staticFactory");
staticFactory.say();
方法三：使用实例工厂方法实例化bean
java代码：
package com.test; import com.dao.UserDao;
import com.dao.impl.UserDaoImpl; public class InstanceBean {
private static UserDao userDaoA = new UserDaoImpl(); //该方法必须是非静态的
public UserDao getBeanInstance() {
return userDaoA;
} }
接口UserDao：
package com.dao; import com.model.User; public interface UserDao {
public void add(User user);
public void findByid(String id);
} 实现类UserDaoImpl：
package com.dao.impl; import com.dao.UserDao;
import com.model.User; public class UserDaoImpl implements UserDao { private String hello;
@Override
public void add(User user) {
System.out.println("方法三：qwqwqwq!!!");
} @Override
public void findByid(String id) { } public String getHello() {
return hello;
} public void setHello(String hello) {
this.hello = hello;
} }
配置文件：
<!--方法三：使用实例工厂方法实例化bean -->
<bean id="instanceBean" class="com.test.InstanceBean"/>
<bean id="userDaoA" factory-bean="instanceBean" factory-method="getBeanInstance"></bean>
测试代码：
ApplicationContext applicationContext = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml"});
//方法三：使用实例工厂方法实例化bean
UserDao userDao = (UserDao)applicationContext.getBean("userDao");
String username = "pppp";
userDao.add(new User(username));