【Spring】004-Spring依赖注入

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訾博ZiBo 2023-02-24 11:22:54 博主文章分类：Spring ©著作权

文章标签 spring java xml User 文章分类 HarmonyOS 后端开发

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一、构造器注入

（前面已详述，不再赘述）

二、Set方式注入【重点】

1、依赖

bean对象的创建依赖于容器；

2、注入

bean对象所有的属性，由容器注入；

3、环境搭建

第一步：创建实体类Address

package com.zibo.pojo;

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 + '\'' +
                '}';
    }
}

第二步：创建实体类Student

package com.zibo.pojo;

import java.util.*;

public class Student {
    private String name;
    private Address address;
    private String[] books;
    private List<String> habits;
    private Map<String,String> card;
    private Set<String> games;
    private Properties info;
    private String wife;

    public String getName() {
        return name;
    }

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

    public Address getAddress() {
        return address;
    }

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

    public String[] getBooks() {
        return books;
    }

    public void setBooks(String[] books) {
        this.books = books;
    }

    public List<String> getHabits() {
        return habits;
    }

    public void setHabits(List<String> habits) {
        this.habits = habits;
    }

    public Map<String, String> getCard() {
        return card;
    }

    public void setCard(Map<String, String> card) {
        this.card = card;
    }

    public Set<String> getGames() {
        return games;
    }

    public void setGames(Set<String> games) {
        this.games = games;
    }

    public Properties getInfo() {
        return info;
    }

    public void setInfo(Properties info) {
        this.info = info;
    }

    public String getWife() {
        return wife;
    }

    public void setWife(String wife) {
        this.wife = wife;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", address=" + address +
                ", books=" + Arrays.toString(books) +
                ", habits=" + habits +
                ", card=" + card +
                ", games=" + games +
                ", info=" + info +
                ", wife='" + wife + '\'' +
                '}';
    }
}

第三步：编写配置文件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 http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="student" class="com.zibo.pojo.Student">
        <property name="name" value="訾博"/>
    </bean>
</beans>

第四步：编写测试类

package com.zibo;

import com.zibo.pojo.Student;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Student student = context.getBean("student", Student.class);
        System.out.println(student.getName());
    }
}

测试结果：

訾博

4、注入其他类型的数据

第一步：修改配置文件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 http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="student" class="com.zibo.pojo.Student">
        <!--1、普通值注入-->
        <property name="name" value="訾博"/>
        <!-- 2、bean注入-->
        <property name="address" ref="address"/>
        <!--3、数组注入-->
        <property name="books">
            <array>
                <value>Java核心技术</value>
                <value>增长黑客</value>
                <value>Spring MVC学习指南</value>
            </array>
        </property>
        <!--4、list集合注入-->
        <property name="habits">
            <list>
                <value>写代码</value>
                <value>看电影</value>
                <value>读书</value>
            </list>
        </property>
        <!--5、map集合注入-->
        <property name="card">
            <map>
                <entry key="身份认证号" value="123456"/>
                <entry key="银行卡号" value="1357"/>
                <entry key="学号" value="2468"/>
            </map>
        </property>
        <!--6、set集合注入-->
        <property name="games">
            <set>
                <value>CF</value>
                <value>DNF</value>
                <value>LOL</value>
            </set>
        </property>
        <!--7、Properties注入-->
        <property name="info">
            <props>
                <!--也是key与value，只是要注意书写的位置-->
                <prop key="stuNum">123456</prop>
                <prop key="age">22</prop>
            </props>
        </property>
        <!--8、null注入-->
        <property name="wife">
            <null/>
        </property>
    </bean>
    <bean id="address" class="com.zibo.pojo.Address">
        <property name="address" value="河南省郑州市"/>
    </bean>
</beans>

第二步：修改测试类

package com.zibo;

import com.zibo.pojo.Student;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Student student = context.getBean("student", Student.class);
        System.out.println(student.toString());
    }
}

测试结果（为便于查看，已手动换行）：

Student{name='訾博', address=Address{address='河南省郑州市'}, books=[Java核心技术, 增长黑客,
 Spring MVC学习指南], habits=[写代码, 看电影, 读书], card={身份认证号=123456, 银行卡号=1357, 
学号=2468}, games=[CF, DNF, LOL], info={stuNum=123456, age=22}, wife='null'}

三、拓展方式

1、p命名空间注入

第一步：创建实体类User

package com.zibo.pojo;

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

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

第二步：创建新的配置文件newBeans.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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://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-->
    <!--p命名空间注入：用于无参构造注入-->
    <bean id="user" class="com.zibo.pojo.User" p:name="訾博" p:age="24"/>
</beans>

第三步：修改测试类

package com.zibo;

import com.zibo.pojo.User;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("newBeans.xml");
        User user = context.getBean("user", User.class);
        System.out.println(user.toString());
    }
}

测试结果：

User{name='訾博', age=24}

2、c命名空间注入

第一步：修改实体类User

package com.zibo.pojo;

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

    public User() {

    }

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

第二步：修改配置文件newBeans.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:c="http://www.springframework.org/schema/c"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd">
    <!--c命名空间注入：用于带参构造注入-->
    <!--c命名空间注入，可以直接注入属性的值：下标、属性都行-->
    <bean id="user" class="com.zibo.pojo.User" c:_0="訾博" c:_1="24"/>
</beans>

测试结果：

User{name='訾博', age=24}

注意：

导入命名空间的相关约束；

四、Bean的作用域

1、官方文档截图

【Spring】004-Spring依赖注入_User

2、singleton单例模式（默认）

当配置文件被加载时创建所有bean对象，仅创建一次，以后无论调用多少次，所调用的都是同一个对象；

不再代码演示，可参考前面笔记：【Spring】002-探索Spring IOC创建对象的方式

3、prototype多例模式

第一步：创建一个实体类People

package com.zibo.pojo;

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

    public People() {
        System.out.println("无参执行了！");
    }

    public People(String name, int age) {
        this.name = name;
        this.age = age;
        System.out.println("带参执行了！");
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "People{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

第二步：新建配置文件peopleBean.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 http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="people" class="com.zibo.pojo.People" scope="prototype">
        <property name="name" value="訾博"/>
        <property name="age" value="24"/>
    </bean>
</beans>

第三步：修改测试类

package com.zibo;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        new ClassPathXmlApplicationContext("peopleBean.xml");
    }
}

测试结果：

【Spring】004-Spring依赖注入_User_02

第四步：修改测试类，获取对象并使用

package com.zibo;

import com.zibo.pojo.People;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("peopleBean.xml");
        People people = context.getBean("people", People.class);
        System.out.println(people.toString());
    }
}

测试结果：

无参执行了！
People{name='訾博', age=24}

说明了什么：

说明在被使用时创建对象；

第五步：修改测试类，再获取一个对象，看是否是同一个对象

package com.zibo;

import com.zibo.pojo.People;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("peopleBean.xml");
        People people = context.getBean("people", People.class);
        People people1 = context.getBean("people", People.class);
        System.out.println(people == people1);
    }
}

测试结果：

无参执行了！
无参执行了！
false

结论：

多例模式，配置文件被加载的时候并不立即创建对象，而是等到对象被获取的时候进行创建，且每次获取都会进行实例化，所获取到的不是同一个对象；

4、其他

正在web中使用到，暂不做探究；

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