依赖注入

依赖注入

声明：本文章属于学习笔记，根据狂神说的Spring编写

Spring官方文档：Spring官方文档

一丶依赖注入：

依赖注入（Dependency Injection），是这样一个过程：由于某客户类只依赖于服务类的一个接口，而不依赖于具体服务类，所以客户类只定义一个注入点。在程序运行过程中，客户类不直接实例化具体服务类实例，而是客户类的运行上下文环境或专门组件负责实例化服务类，然后将其注入到客户类中，保证客户类的正常运行。

二丶DI依赖注入环境

首先我们看这两个实体类：

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

public class Student {
    private String name;
    private Address address;
    private String[] books;
    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[] getBooks() {
        return books;
    }

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

    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() +
                ", books=" + Arrays.toString(books) +
                ", hobbys=" + hobbys +
                ", card=" + card +
                ", games=" + games +
                ", wife='" + wife + '\'' +
                ", info=" + info +
                '}';
    }
}

之后配置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
        https://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="stu" class="com.kdy.pojo.Student">
        <property name="name" value="kdy"/>
    </bean>
</beans>

测试类测试：

public class MyTest {
    @Test
    public void test(){
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        Student stu = (Student)context.getBean("stu");
        System.out.println(stu.getName());
    }
}

运行结果：

三丶依赖注入之set注入

我们还是来用student类来进行set的注入。

beans.xml文件的配置：

<?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.kdy.pojo.Address"></bean>
    <bean id="stu" class="com.kdy.pojo.Student">
        <property name="name" value="kdy"/>

        <property name="address" ref="address"/>
        <!--数组-->
        <property name="books">
            <array>
                <value>西游记</value>
                <value>红楼梦</value>
            </array>
        </property>

        <!--list-->
        <property name="hobbys">
            <list>
                <value>抽烟</value>
                <value>喝酒</value>
                <value>烫头</value>
                <value>打游戏</value>
            </list>
        </property>
        <property name="card">
            <map>
                <entry key="姓名" value="kdy" />
                <entry key="学号" value="041940223" />
            </map>
        </property>
        <property name="games">
            <set>
                <value>lol</value>
                <value>cf</value>
                <value>dnf</value>
            </set>
        </property>
        <property name="wife">
            <null/>
        </property>
        <property name="info">
            <props>
                <prop key="name" > kdy</prop>
                <prop key="password" > kdy1</prop>
                <prop key="lll" > kdy2</prop>
            </props>
        </property>
    </bean>
</beans>

测试类测试：

   @Test
    public void test(){
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        Student stu = (Student)context.getBean("stu");
        System.out.println(stu.toString());
    }

运行结果：

Student{name=‘kdy’, address=Address{address=‘null’}, books=[西游记, 红楼梦], hobbys=[抽烟, 喝酒, 烫头, 打游戏], card={姓名=kdy, 学号=041940223}, games=[lol, cf, dnf], wife=‘null’, info={password=kdy1, name=kdy, lll=kdy2}}

四丶c命名和p命名空间注入

首先如果我们要使用这个c命名或者是p命名空间注入，那么就必须要引入标签连接：

xmlns:p=“http://www.springframework.org/schema/p”
xmlns:c=“http://www.springframework.org/schema/c”

userbeans.xml文件配置：

运行结果：