Spring - 4.Spring之DI(聚合对象注入) - 《Java笔记》

如果某一个属性中需要赋值空对象 null对象而非是”null”———我们可以利用

如果某一个属性中带有特殊字符 String类型
需要利用这个标签来进行操作<![CDATA[xxx]]>
注意:这个标签需要以分层的形式写在中间（标签也是）

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean name="student" class="domain.Student">
        <constructor-arg name="sid" value="1" type="java.lang.Integer"></constructor-arg>
        <constructor-arg name="sname">
            <value><![CDATA[klxh~~]]></value>
        </constructor-arg>
        <constructor-arg name="ssex" value="女" type="java.lang.String"></constructor-arg>
        <constructor-arg name="sage" value="18" type="java.lang.Integer"></constructor-arg>
    </bean>
</beans>

我们正常开发中，需要赋值的属性很多时候并不是8大基本类型以及一些原生包装类，而是一些其他对象，可以通过来实现赋值。
例如一个房间中有电脑：
Room

package domain;

public class Room {

    private String name;//机房房间号 属性
    private Computer computer;//机房中有一台电脑 属性 (has a) 聚合 组合 包含

    @Override
    public String toString() {
        return "Room{" +
                "name='" + name + '\'' +
                ", computer=" + computer +
                '}';
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Computer getComputer() {
        return computer;
    }
    public void setComputer(Computer computer) {
        this.computer = computer;
    }
}

Computer

package domain;

public class Computer {

    private String brand;//电脑品牌   ThinkPad
    private String name;//电脑型号    S5
    private Float price;//电脑价格    8000

    public Computer() {
    }

    public Computer(String brand, String name, Float price) {
        this.brand = brand;
        this.name = name;
        this.price = price;
    }


    @Override
    public String toString() {
        return "Computer{" +
                "brand='" + brand + '\'' +
                ", name='" + name + '\'' +
                ", price=" + price +
                '}';
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setPrice(Float price) {
        this.price = price;
    }

    public String getBrand() {
        return brand;
    }
    public String getName() {
        return name;
    }
    public Float getPrice() {
        return price;
    }
}

ApplicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean name="computer" class="domain.Computer">
        <constructor-arg name="brand" value="ThinkPad"></constructor-arg>
        <constructor-arg name="name" value="s5"></constructor-arg>
        <constructor-arg name="price" value="8000"></constructor-arg>
    </bean>
    <bean name="room" class="domain.Room">
        <property name="name" value="001"></property>
        <property name="computer" ref="computer"></property>
    </bean>

</beans>

如果对象里面的那个属性对象是私有的，不想别其他人访问，我们可以采用内部bean的写法

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean name="room" class="domain.Room">
        <property name="name" value="001"></property>

        <property name="computer">
            <bean class="domain.Computer">
                <constructor-arg name="brand" value="ThinkPad"></constructor-arg>
                <constructor-arg name="name" value="s5"></constructor-arg>
                <constructor-arg name="price" value="8000"></constructor-arg>
            </bean>
        </property>

    </bean>

</beans>

Controller—-Service—-Dao
StudentController

package controller;

import service.StudentService;

public class StudentController {

    private StudentService service;
    public StudentController(StudentService service) {
        this.service = service;
    }

    public void login(){
        System.out.println("controller层接收请求信息");
        //获取请求发送过来的信息
        //调用service去处理业务---->
        service.login();
        //根据service处理的结果 给予响应
        System.out.println("controller层给予响应");
    }
}

StudentService

package service;

import dao.StudentDao;

public class StudentService {

    private StudentDao dao;
    public StudentService(StudentDao dao) {
        this.dao = dao;
    }

    public void login(){
        //1.方法应该有参数  Controller传递给我的
        System.out.println("service层接收请求发来的信息");
        //2.做一些业务处理  判断   dao调用查询方法----->
        dao.selectOne();
        //3.将判断的结果返回
        System.out.println("service层处理业务并返回");
    }
}

StudentDao

package dao;

import domain.Student;

public class StudentDao {

    public Student selectOne(){
        //1.方法里面有参数 service层给我的
        System.out.println("dao层接收service层传递的信息");
        //2.自己写一条Sql语句
        System.out.println("执行数据库操作");
        //3.调用SqlSession做事就可以了
        System.out.println("将查询的结果返回");
        return null;
    }
}

TestMain

package test;

import controller.StudentController;
import domain.Room;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestMain {
    public static void main(String[] args){
        //演示Spring的DI
        BeanFactory factory=new ClassPathXmlApplicationContext("ApplicationContext.xml");
        StudentController controller=(StudentController)factory.getBean("controller") ;
        controller.login();

    }
}

ApplicationContext.xml
写法一：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean name="controller" class="controller.StudentController">
        <constructor-arg name="service">
            <bean name="service" class="service.StudentService">
                <constructor-arg name="dao">
                    <bean name="dao" class="dao.StudentDao"></bean>
                </constructor-arg>
            </bean>
        </constructor-arg>
    </bean>

</beans>

写法二：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean name="controller" class="controller.StudentController">
        <constructor-arg name="service" ref="service"></constructor-arg>
    </bean>
    <bean name="service" class="service.StudentService">
        <constructor-arg name="dao" ref="dao"></constructor-arg>
    </bean>
    <bean name="dao" class="dao.StudentDao"></bean>

</beans>