Spring 依赖注入

6. 依赖注入

6.1 构造器注入

前面已经说过

6.2 set方式注入※

依赖注入：本质是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

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

真实测试对象

package com.peng.pojo;

import java.util.*;

public class Student {
    private String name;
    private Address address;
    private String[] book;
    private List<String> hobbys;
    private Map<String,String> card;
    private Set<String> games;
    private String wife;
    private Properties 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[] getBook() {
        return book;
    }

    public void setBook(String[] book) {
        this.book = book;
    }

    public List<String> getHobbys() {
        return hobbys;
    }

    public void setHobbys(List<String> hobbys) {
        this.hobbys = hobbys;
    }

    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 Properties getInfo() {
        return info;
    }

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

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

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
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="address" class="com.peng.pojo.Address">
        <property name="address" value="葫芦岛"/>
    </bean>
    <bean id="student" class="com.peng.pojo.Student">
        <!--1.普通值注入，value-->
        <property name="name" value="peng"/>

        <!--2.其他高级类型注入，bean注入，ref-->
        <property name="address" ref="address"/>

        <!--3.数组注入，ref-->
        <property name="book">
            <array>
                <value>红楼梦</value>
                <value>西游记</value>
                <value>水浒传</value>
                <value>三国演义</value>
            </array>
        </property>

        <!--4.List-->
        <property name="hobbys">
            <list>
                <value>吃饭</value>
                <value>睡觉</value>
            </list>
        </property>

        <!--5.Map-->
        <property name="card">
            <map>
                <entry key="身份证" value="132151313213513553"/>
                <entry key="银行卡" value="165562612020201234"/>
            </map>
        </property>

        <!--6.Set-->
        <property name="games">
            <set>
                <value>LOL</value>
                <value>CF</value>
            </set>
        </property>

        <!--7.null，空值注入-->
        <property name="wife">
            <null/>
        </property>
        
        <!--8.Properties-->
        <property name="info">
            <props>
                <prop key="学号">20200525</prop>
                <prop key="性别">男</prop>
                <prop key="生日">20010604</prop>
            </props>
        </property>
    </bean>
</beans>

测试类

import com.peng.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.toString());
    }
}

输出

Student{name='peng', address=Address{address='葫芦岛'}, book=[红楼梦, 西游记, 水浒传, 三国演义], hobbys=[吃饭, 睡觉], card={身份证=132151313213513553, 银行卡=165562612020201234}, games=[LOL, CF], wife='null', info={学号=20200525, 生日=20010604, 性别=男}}

6.3 其他方式

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

User.java

package com.peng.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 +
                '}';
    }
}

userbeans.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="com.peng.pojo.User" p:name="peng" p:age="18"/>
    <!--c命名空间注入，通过构造器注入，constructor-->
    <bean id="user2" class="com.peng.pojo.User" c:age="18" c:name="peng"/>
</beans>

测试类

import com.peng.pojo.User;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        test2();
        test3();
    }

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

    @Test
    public static void test3(){
        ApplicationContext context = new ClassPathXmlApplicationContext("userbeans.xml");
        User user = context.getBean("user2",User.class);
        System.out.println(user);
    }
}