Spring笔记（四）：依赖注入（DI）

 

时间：2021/10/25

 

下面我们将对不同类型的属性通过spring的bean容器实现赋值：

1.编写实体类

Address实体类：

package bupt.machi.pojo;

public class Address {

    private String city;

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

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

Student实体类：

package bupt.machi.pojo;

import java.util.*;

public class Student {

    private String name;
    private Address address;
    private String[] hobbys;

    public void setHobbys(String[] hobbys) {
        this.hobbys = hobbys;
    }

    public String[] getHobbys() {
        return hobbys;
    }

    private List<String> books;
    private Map<String, Integer> scores;
    private Set<String> games;
    private Properties properties;
    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 List<String> getBooks() {
        return books;
    }

    public void setBooks(List<String> books) {
        this.books = books;
    }

    public Map<String, Integer> getScores() {
        return scores;
    }

    public void setScores(Map<String, Integer> scores) {
        this.scores = scores;
    }

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

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

    public Properties getProperties() {
        return properties;
    }

    public void setProperties(Properties properties) {
        this.properties = properties;
    }

    public String getWife() {
        return wife;
    }

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

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

 

2.编写spring配置文件

<?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="address" class="bupt.machi.pojo.Address">
        <property name="city" value="qingdao"/>
    </bean>

    <bean id="student" class="bupt.machi.pojo.Student">
        <property name="name" value="machi"/>
<!--   引用     -->
        <property name="address" ref="address"/>
<!--   数组     -->
        <property name="hobbys">
            <array>
                <value>学习</value>
                <value>写代码</value>
                <value>睡觉</value>
            </array>
        </property>
<!--   list     -->
        <property name="books">
            <list>
                <value>黄金时代</value>
                <value>冰与火之歌</value>
            </list>
        </property>
<!--   map     -->
        <property name="scores">
            <map>
                <entry key="数学" value="100"/>
                <entry key="语文" value="100"/>
            </map>
        </property>
<!--   set     -->
        <property name="games">
            <set>
                <value>英雄联盟</value>
                <value>王者荣耀</value>
            </set>
        </property>
<!--   properties     -->
        <property name="properties">
            <props>
                <prop key="性别">男</prop>
                <prop key="爱好">女</prop>
            </props>
        </property>
<!--   null     -->
        <property name="wife">
            <null/>
        </property>
    </bean>
</beans>

 

3.编写测试类

import bupt.machi.pojo.Student;
import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {

    @Test
    public void testStudent(){
        ApplicationContext classPathXmlApplicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");

        Student student = (Student) classPathXmlApplicationContext.getBean("student");
        System.out.println(student);
    }
}

 

4.总结

依赖注入的方式：

• 构造器注入（通过有参构造方法给属性赋值）
• Set方式注入
• 拓展方式注入（通过p命名空间和c命名空间，不能直接使用，需要导入xml约束）