Spring框架怎样使用P命名空间进行注入

package dao;

import entity.User;

/**
 * 增加DAO接口,定义了所需的持久化方法
 */
public interface UserDao {
  public void save(User user);
}

package dao.impl;

import dao.UserDao;
import entity.User;

/**
 * 用户DAO类，实现IDao接口，负责User类的持久化操作
 */
public class UserDaoImpl implements UserDao {

  public void save(User user) {
    // 这里并未实现完整的数据库操作，仅为说明问题
    System.out.println("保存用户信息到数据库");
  }
}

package service;

import entity.User;

/**
 * 用户业务接口，定义了所需的业务方法
 */
public interface UserService {
  public void addNewUser(User user);
}

package service.impl;

import service.UserService;
import dao.UserDao;
import entity.User;

/**
 * 用户业务类，实现对User功能的业务管理
 */
public class UserServiceImpl implements UserService {

  // 声明接口类型的引用，和具体实现类解耦合
  private UserDao dao;

  

  // 生成无参构造方法
  public UserServiceImpl() {

  }

  // 带参数构造方法  为dao进行赋值
  public UserServiceImpl(UserDao dao) {
    this.dao = dao;
  }


  public UserDao getDao() {
    return dao;
  }

  // dao 属性的setter访问器，会被Spring调用，实现设值注入
  public void setDao(UserDao dao) {
    this.dao = dao;
  }

  public void addNewUser(User user) {
    // 调用用户DAO的方法保存用户信息
    dao.save(user);
    System.out.println("注入进去的user对象的信息是："+user.toString());
  }
}

package entity;

/**
 * 用户实体类
 */
public class User implements java.io.Serializable {
  private Integer id; // 用户ID
  private String username; // 用户名
  private String password; // 密码
  private String email; // 电子邮件
  private int age;//年龄
  

  @Override
  public String toString() {
    return "User [id=" + id + ", username=" + username + ", password="
        + password + ", email=" + email + ", age=" + age
        + ", getAge()=" + getAge() + ", getId()=" + getId()
        + ", getUsername()=" + getUsername() + ", getPassword()="
        + getPassword() + ", getEmail()=" + getEmail()
        + ", getClass()=" + getClass() + ", hashCode()=" + hashCode()
        + ", toString()=" + super.toString() + "]";
  }

  public int getAge() {
    return age;
  }

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

  // getter & setter
  public Integer getId() {
    return id;
  }

  public void setId(Integer id) {
    this.id = id;
  }

  public String getUsername() {
    return username;
  }

  public void setUsername(String username) {
    this.username = username;
  }

  public String getPassword() {
    return password;
  }

  public void setPassword(String password) {
    this.password = password;
  }

  public String getEmail() {
    return email;
  }

  public void setEmail(String email) {
    this.email = email;
  }

}

package test;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import service.UserService;
import service.impl.UserServiceImpl;

import entity.User;


public class AopTest {

  @Test
  public void aopTest() {
    ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
    UserService service = (UserService) ctx.getBean("userService");
    User user = (User) ctx.getBean("user");
    service.addNewUser(user);
  }

}