【Spring】004-Spring依赖注入
【Spring】004-Spring依赖注入
訾博ZiBo
发布于 2025-01-06 07:44:28
发布于 2025-01-06 07:44:28
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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
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：
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；
本文参与 腾讯云自媒体同步曝光计划，分享自作者个人站点/博客。
原始发表：2025-01-06，如有侵权请联系 cloudcommunity@tencent.com 删除
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