Spring——创建对象、配置及依赖注入4.IOC创建对象的方式5.Spring配置DI依赖注入

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我是靠谱客的博主开放过客，最近开发中收集的这篇文章主要介绍Spring——创建对象、配置及依赖注入4.IOC创建对象的方式5.Spring配置DI依赖注入，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

文章目录

4.IOC创建对象的方式
5.Spring配置
- 别名
- Bean的配置
- import
DI依赖注入
- 构造器注入
- Set方式注入!!!!
- 拓展方式注入
- Bean的作用域

4.IOC创建对象的方式

使用无参构造创建对象，默认！

假设我们要使用有参构造创建对象

下标赋值

<bean id="user" class="net.cqwu.pojo.User">
            <constructor-arg index="0" value="feliks"/>
        </bean>

类型赋值：不建议使用

    <bean id="user" class="net.cqwu.pojo.User">
        <constructor-arg type="java.lang.String" value="feliks2"/>
    </bean>

参数名

    <bean id="user" class="net.cqwu.pojo.User">
        <constructor-arg name="name" value="feliks3"/>
    </bean>

总结：在配置文件加载的时候，容器中管理的对象就已经初始化了

User

public class User {
    private String name;

    //没有无参构造，报错
    public User(String name){
        this.name = name;
    }
//省略getter,setter
    public void show(){
        System.out.println("name:"+name);
    }
}

applicationContext.xml配置

<?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">

<!--    1.下标赋值-->
<!--        <bean id="user" class="net.cqwu.pojo.User">-->
<!--            <constructor-arg index="0" value="feliks"/>-->
<!--        </bean>-->

<!--    2.类型赋值法：不建议使用-->
<!--    <bean id="user" class="net.cqwu.pojo.User">-->
<!--        <constructor-arg type="java.lang.String" value="feliks2"/>-->
<!--    </bean>-->

<!--3.直接通过参数名来创建-->
    <bean id="user" class="net.cqwu.pojo.User">
        <constructor-arg name="name" value="feliks3"/>
    </bean>

    <bean id="userT" class="net.cqwu.pojo.UserT"></bean>
</beans>

测试MyTest

import net.cqwu.pojo.User;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {

       //Spring容器，类似于婚介网站
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

        User user = (User) context.getBean("user");
        User user2 = (User) context.getBean("user");
        user.show();
        System.out.println(user == user2);
    }
}

5.Spring配置

别名

<!--    如果添加了别名，也可以使用别名获取这个对象-->
    <alias name="user" alias="bieming"/>

Bean的配置

<!--
    id: bean 的唯一标识符，相当于对象名
    class: bean 对象所对应的全限定名：包名 + 类名
    name: 别名
-->
    <bean id="userT" class="net.cqwu.pojo.UserT" name="user2">
        <property name="name" value="feliks"></property>
    </bean>

UserT user = (UserT) context.getBean("user2");
        user.show();

import

团队开发时，将多个配置文件导入合并为一个

<import resource="beans1.xml"></import>

DI依赖注入

构造器注入

<beans>
    <bean id="beanOne" class="x.y.ThingOne">
        <constructor-arg ref="beanTwo"/>
        <constructor-arg ref="beanThree"/>
    </bean>

    <bean id="beanTwo" class="x.y.ThingTwo"/>

    <bean id="beanThree" class="x.y.ThingThree"/>
</beans>

Set方式注入!!!

依赖注入：set注入
- 依赖：bean对象的创建依赖于容器
- 注入：bean对象中的所有属性，由容器来注入

【环境搭建】

复杂类型

public class Address {
    private String address;

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "Address{" +
                "address='" + address + ''' +
                '}';
    }
}

真实测试对象

public class Student {

    private String name;
    private Address address;
    private String[] books;
    private List<String> hobbys;
    private Map<String,String> card;
    private Set<String> game;
    private String wife;//空指针
    private Properties info;
}
//get  set  toString省略

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 id="address" class="net.cqwu.pojo.Address">
        <property name="address" value="Chongqing"></property>
    </bean>
    <bean id="student" class="net.cqwu.pojo.Student">
    <!--第一种：普通值注入 -->
    <property name="name" value="feliks"></property>

    <!--第二种：Bean注入：ref-->
        <property name="address" ref="address"></property>

    <!--数组注入-->
        <property name="books">
            <array>
                <value>西游记</value>
                <value>红楼梦</value>
                <value>三国</value>
                <value>水浒</value>
            </array>
        </property>

        <!--List注入-->
        <property name="hobbys">
            <list>
                <value>魔方</value>
                <value>唱歌</value>
                <value>听歌</value>
            </list>
        </property>

        <!--Map-->
        <property name="card">
            <map>
                <entry key="身份证" value="11111111"/>
                <entry key="银行卡" value="22222222"/>
            </map>
        </property>

        <!--Set-->
        <property name="game">
            <set>
                <value>lol</value>
                <value>bob</value>
                <value>coc</value>
            </set>
        </property>

        <!--null-->
        <property name="wife">
            <null/>
        </property>

        <!--Properties-->
        <property name="info">
            <props>
                <prop key="学号">4029</prop>
                <prop key="姓名">feliks</prop>
                <prop key="专业">软件</prop>
                <prop key="username">admin</prop>
                <prop key="password">123456</prop>
            </props>
        </property>

    </bean>
</beans>

MyTest

public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Student student = (Student) context.getBean("student");
        System.out.println(student.toString());
    }
}
/*
* Student{
name='feliks'
, address=Address{address='Chongqing'}
, books=[西游记, 红楼梦, 三国, 水浒]
, hobbys=[魔方, 唱歌, 听歌]
, card={身份证=11111111, 银行卡=22222222}
, game=[lol, bob, coc]
, wife='null'
, info={学号=4029, password=123456, 专业=软件, 姓名=feliks, username=admin}
}
* */

拓展方式注入

详细解释见官方文档中的

XML Shortcut with the p-namespace
XML Shortcut with the c-namespace

对象

public class User {
    private String name;
    private int age;


    //加上无参 和 有参构造器，才能使用c命名注入
    public User() {
    }

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }
}//省略getter setter toString

测试类

    @Test
    public void test2() {
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        User user = context.getBean("user2",User.class);
        System.out.println(user);
    }

beans.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"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:c="http://www.springframework.org/schema/c"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

        <!--p命名空间注入，可以直接注入属性的值：property-->
        <bean id="user" class="net.cqwu.pojo.User" p:name="feliks" p:age="22"/>

        <!--c命名空间注入，通过构造器注入：constructs-args-->
        <bean id="user2" class="net.cqwu.pojo.User" c:age="21" c:name="Feliks"/>
</beans>

注意：p 和 c命名空间注入不能直接使用，需要导入xml约束

xmlns:p="http://www.springframework.org/schema/p"
xmlns:c="http://www.springframework.org/schema/c"

Bean的作用域

官方文档：

Scope	Description
singleton	(Default) Scopes a single bean definition to a single object instance for each Spring IoC container.
prototype	Scopes a single bean definition to any number of object instances.
request	Scopes a single bean definition to the lifecycle of a single HTTP request. That is, each HTTP request has its own instance of a bean created off the back of a single bean definition. Only valid in the context of a web-aware Spring `ApplicationContext`.
session	Scopes a single bean definition to the lifecycle of an HTTP `Session`. Only valid in the context of a web-aware Spring `ApplicationContext`.
application	Scopes a single bean definition to the lifecycle of a `ServletContext`. Only valid in the context of a web-aware Spring `ApplicationContext`.
websocket	Scopes a single bean definition to the lifecycle of a `WebSocket`. Only valid in the context of a web-aware Spring `ApplicationContext`.

单例模式（Spring默认机制）

<bean id="user2" class="net.cqwu.pojo.User" c:age="21" c:name="Feliks" scope="singleton"/>

测试

        User user = context.getBean("user2",User.class);
        User user2 = context.getBean("user2",User.class);
        System.out.println(user==user2);//true

原型模式：每次从容器中get的时候，都会产生一个新对象

<bean id="user2" class="net.cqwu.pojo.User" c:age="21" c:name="Feliks" scope="prototype"/>

测试

        User user = context.getBean("user2",User.class);
        User user2 = context.getBean("user2",User.class);
        System.out.println(user==user2);//false