Spring快速入门-04-依赖注入（DI）

redemption_2

已于 2024-11-03 10:05:01 修改

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分类专栏： spring快速入门文章标签： spring java

于 2024-11-03 10:03:45 首次发布

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6 篇文章

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6. 依赖注入（DI）

6.1. 构造器注入

见4.IoC创建对象方式

6.2. Set注入（重点）

依赖注入（Set注入！）：注入Bean对象的属性

依赖：Bean对象的创建依赖于容器
注入：Bean对象中的所有属性，由容器来设置和装配

6.2.1. 案例，普通值注入

案例环境搭建

Address.java实体类，Student.java实体类

package com.kuang.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 + '\'' +
        '}';
    }
}

package com.kuang.pojo;

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Set;

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

    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> getHobby() {
        return hobby;
    }

    public void setHobby(List<String> hobby) {
        this.hobby = hobby;
    }

    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 String getWife() {
        return wife;
    }

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

    public String getInfo() {
        return info;
    }

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

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

spring配置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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="student" class="com.kuang.pojo.Student">
        <!-- 第一种：普通值注入，value -->
        <property name="name" value="kuang"/>
    </bean>

</beans>

测试

import com.kuang.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("beans.xml");
        Student student = (Student) context.getBean("student");
        System.out.println(student.getName());
    }
}

6.2.2. Bean注入

这里的值是一个引用，ref

<?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="com.kuang.pojo.Address">
    <property name="address" value="北京"/>
  </bean>

  <bean id="student" class="com.kuang.pojo.Student">
    <!-- 第一种：普通值注入，value -->
    <property name="name" value="kuang"/>
    <!-- 第二种：bean注入，ref -->
    <property name="address" ref="address"/>
  </bean>

</beans>

import com.kuang.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("beans.xml");
        Student student = (Student) context.getBean("student");
        System.out.println(student.getName());
        System.out.println(student.getAddress());
    }
}

6.2.3. 数组注入

<?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="com.kuang.pojo.Address">
    <property name="address" value="北京"/>
  </bean>

  <bean id="student" class="com.kuang.pojo.Student">
    <!-- 第一种：普通值注入，value -->
    <property name="name" value="kuang"/>
    <!-- 第二种：bean注入，ref -->
    <property name="address" ref="address"/>
    <!-- 第三种：数组注入 -->
    <property name="books">
      <array>
        <value>红楼梦</value>
        <value>西游记</value>
        <value>水浒传</value>
        <value>三国演义</value>
      </array>
    </property>
  </bean>

</beans>

import com.kuang.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("beans.xml");
        Student student = (Student) context.getBean("student");
        System.out.println(student.getName());
        System.out.println(student.getAddress());
        for (String book : student.getBooks()) {
            System.out.println(book);
        }
    }
}

6.2.4. List注入

<?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="com.kuang.pojo.Address">
        <property name="address" value="北京"/>
    </bean>

    <bean id="student" class="com.kuang.pojo.Student">
        <!-- 第一种：普通值注入，value -->
        <property name="name" value="kuang"/>
        <!-- 第二种：bean注入，ref -->
        <property name="address" ref="address"/>
        <!-- 第三种：数组注入 -->
        <property name="books">
            <array>
                <value>红楼梦</value>
                <value>西游记</value>
                <value>水浒传</value>
                <value>三国演义</value>
            </array>
        </property>
        <!-- 第四种：List注入 -->
        <property name="hobby">
            <list>
                <value>听歌</value>
                <value>看电影</value>
                <value>编程</value>
            </list>
        </property>
    </bean>

</beans>

import com.kuang.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("beans.xml");
        Student student = (Student) context.getBean("student");
        System.out.println(student.getName());
        System.out.println(student.getAddress());
        for (String book : student.getBooks()) {
            System.out.println(book);
        }
        System.out.println();
        for (String hobby : student.getHobby()) {
            System.out.println(hobby);
        }
    }
}

6.2.5. Map注入

<?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="com.kuang.pojo.Address">
        <property name="address" value="北京"/>
    </bean>

    <bean id="student" class="com.kuang.pojo.Student">
        <!-- 第一种：普通值注入，value -->
        <property name="name" value="kuang"/>
        <!-- 第二种：bean注入，ref -->
        <property name="address" ref="address"/>
        <!-- 第三种：数组注入 -->
        <property name="books">
            <array>
                <value>红楼梦</value>
                <value>西游记</value>
                <value>水浒传</value>
                <value>三国演义</value>
            </array>
        </property>
        <!-- 第四种：List注入 -->
        <property name="hobby">
            <list>
                <value>听歌</value>
                <value>看电影</value>
                <value>编程</value>
            </list>
        </property>
        <!-- 第五种：Map注入 -->
        <property name="card">
            <map>
                <entry key="身份证" value="1234567890"/>
                <entry key="银行卡" value="0987654321"/>
            </map>
        </property>
    </bean>

</beans>

import com.kuang.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("beans.xml");
        Student student = (Student) context.getBean("student");
        System.out.println(student.getName());
        System.out.println(student.getAddress());
        for (String book : student.getBooks()) {
            System.out.println(book);
        }
        System.out.println();
        for (String hobby : student.getHobby()) {
            System.out.println(hobby);
        }
        System.out.println();
        System.out.println(student.getCard());

    }
}

6.2.6. set注入

<!-- 第六种：Set注入 -->
        <property name="games">
            <set>
                <value>LOL</value>
                <value>CF</value>
                <value>DNF</value>
            </set>
        </property>

ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
Student student = (Student) context.getBean("student");
System.out.println(student.getGames());

6.2.7. Null注入

<!-- 第七种：null注入 -->
        <property name="wife">
            <null/>
        </property>

ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
Student student = (Student) context.getBean("student");
System.out.println(student.getInfo());

6.2.8. Properties注入

修改Student实体类

private Properties info;

public Properties getInfo() {
    return info;
}

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

<!-- 第八种：Properties注入 -->
        <property name="info">
            <props>
                <prop key="学号">20210106</prop>
                <prop key="性别">保密</prop>
                <prop key="姓名">subei</prop>
            </props>
        </property>

ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
Student student = (Student) context.getBean("student");
System.out.println(student.getInfo());