Spring--xml方式实现DI

作者: aruba | 来源:发表于2022-05-18 13:34 被阅读0次

作为SSM框架中的一个，Spring框架和Dagger一样，它是一个IOC容器，除此以外还支持AOP编程。关于IOC，安卓开发中已经介绍过了，简单来说，对象的生产和生命周期的管理都交由容器实现，我们在用到的地方直接注入（DI）即可使用，省去了程序员重复编写创建对象的操作。后期一般使用注解注入，配合apt+javapoet+javassisit可以完全交由注解实现，不需要写xml
xml实现di为最基础的操作，通过编写xml文件，指定生成的对象规则，最后由自定义xml解析器解析xml，并将对象放入容器中，通过容器即可获取对象或者重新生成新对象

一、Spring初步使用

导入依赖：

        <!--包含了一系列组件-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.3.5</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.1</version>
            <scope>test</scope>
        </dependency>

新建一个实体类：

public class User {
    private Integer uid;
    private String username;
    private String password;

    public User() {
    }

    public User(Integer uid, String username, String password) {
        this.uid = uid;
        this.username = username;
        this.password = password;
    }

    public Integer getUid() {
        return uid;
    }

    public void setUid(Integer uid) {
        this.uid = uid;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "uid=" + uid +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

在resources目录下创建一个xml文件：

xml文件内容：

<?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="user" class="com.aruba.bean.User"></bean>
</beans>

测试方法：

    @org.junit.Test
    public void test1() {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
        User user = applicationContext.getBean("user", User.class);
        System.out.println(user);
    }

运行结果：

二、bean标签属性

<bean id="user" class="com.aruba.bean.User" scope="prototype" lazy-init="true" ></bean>

id：获取对象时的key
class：全类名
scope：作用域
singleton 表示全局只有一个，即单例
prototype 表示每次获取都创建一个新的对象
lazy-init：是否开启懒加载，开启后只有在获取对象时才会实例化对象

三、对象属性为基本类型的赋值

1. 构造函数传参

可以通过constructor-arg标签，指定构造函数中的传参：

    <bean id="user2" class="com.aruba.bean.User">
        <constructor-arg name="username" value="xiaoming"></constructor-arg>
        <constructor-arg name="uid" value="1"></constructor-arg>
        <constructor-arg index="2" value="123456"></constructor-arg>
    </bean>

其中name属性对应实体类中的属性名，index属性则对应传参索引

可以通过constructor-arg标签的命名空间简化标签：

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

2. 设置属性传参

可以通过property标签设置对象的属性：

    <bean id="user3" class="com.aruba.bean.User">
        <property name="username" value="赵四"/>
        <property name="uid" value="4"/>
        <property name="password" value="54321"/>
    </bean>

name属性最终是利用反射调用set方法，如果实体类里没有定义对应的set方法，则报错

property标签也可以通过命名空间简化：

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

四、bean引用

上面我们只是对基本类型数据进行了传递和设置，现在给User类新增一个Job的属性

新建Job实体类：

public class Job {
    private Integer jid;
    private String jobName;
    private String jobDescription;

    public Job() {
    }

    @Override
    public String toString() {
        return "Job{" +
                "jid=" + jid +
                ", jobName='" + jobName + '\'' +
                ", jobDescription='" + jobDescription + '\'' +
                '}';
    }

    public Integer getJid() {
        return jid;
    }

    public void setJid(Integer jid) {
        this.jid = jid;
    }

    public String getJobName() {
        return jobName;
    }

    public void setJobName(String jobName) {
        this.jobName = jobName;
    }

    public String getJobDescription() {
        return jobDescription;
    }

    public void setJobDescription(String jobDescription) {
        this.jobDescription = jobDescription;
    }

    public Job(Integer jid, String jobName, String jobDescription) {
        this.jid = jid;
        this.jobName = jobName;
        this.jobDescription = jobDescription;
    }
}

User中新增Job属性：

public class User {
    private Integer uid;
    private String username;
    private String password;
    private Job job;

    public User() {
    }

    public User(Integer uid, String username, String password) {
        this.uid = uid;
        this.username = username;
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "uid=" + uid +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", job=" + job +
                '}';
    }

    public User(Integer uid, String username, String password, Job job) {
        this.uid = uid;
        this.username = username;
        this.password = password;
        this.job = job;
    }

    public Integer getUid() {
        return uid;
    }

    public void setUid(Integer uid) {
        this.uid = uid;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Job getJob() {
        return job;
    }

    public void setJob(Job job) {
        this.job = job;
    }
}

1. 外部引用

xml中定义一个job的bean

    <bean id="job" class="com.aruba.bean.Job" c:_0="1" c:jobName="salesman" c:jobDescription="sale"></bean>

    <bean id="user6" class="com.aruba.bean.User" p:username="赵武" p:uid="6" p:password="789456">
        <property name="job" ref="job"></property>
    </bean>

使用ref指定外部bean

2. 内部引用

bean可以直接在内部创建

    <bean id="user7" class="com.aruba.bean.User" p:username="赵武" p:uid="6" p:password="789456">
        <property name="job">
            <bean class="com.aruba.bean.Job" c:_0="1" c:jobName="salesman" c:jobDescription="sale"></bean>
        </property>
    </bean>

3. 级联引用

外部bean可以在内部设置属性

    <bean id="job2" class="com.aruba.bean.Job"></bean>

    <bean id="user8" class="com.aruba.bean.User" p:username="赵武" p:uid="6" p:password="789456">
        <property name="job" ref="job2"></property>
        <property name="job.jid" value="2"></property>
        <property name="job.jobName" value="algorithm"></property>
        <property name="job.jobDescription" value="algorithm"></property>
    </bean>

五、集合注入

新建一个Skill类：

public class Skill {
    private Integer skilLId;
    private String skilLName;

    @Override
    public String toString() {
        return "Skill{" +
                "skilLId=" + skilLId +
                ", skilLName='" + skilLName + '\'' +
                '}';
    }

    public Integer getSkilLId() {
        return skilLId;
    }

    public void setSkilLId(Integer skilLId) {
        this.skilLId = skilLId;
    }

    public String getSkilLName() {
        return skilLName;
    }

    public void setSkilLName(String skilLName) {
        this.skilLName = skilLName;
    }

    public Skill(Integer skilLId, String skilLName) {
        this.skilLId = skilLId;
        this.skilLName = skilLName;
    }

    public Skill() {
    }
}

User类中添加以下属性，其他代码就不展示了：

    private String[] skills;
    private Skill[] skills2;
    private List<Skill> skillList;
    private Set<Skill> skillSet;
    private Map<String,Skill> skillMap;

1. 数组属性注入

对于字符串或者基本类型的数组：

    <bean id="user9" class="com.aruba.bean.User" p:username="王五" p:uid="7" p:password="789456">
        <property name="skills">
            <array>
                <value>JAVA</value>
                <value>PYTHON</value>
                <value>GO</value>
            </array>
        </property>
    </bean>

数组使用array标签，并且直接使用value

引用类型数组：

    <bean id="user9" class="com.aruba.bean.User" p:username="王五" p:uid="7" p:password="789456">
        <property name="skills2">
            <array>
                <bean class="com.aruba.bean.Skill" c:_0="1" c:_1="JAVA"/>
                <bean class="com.aruba.bean.Skill" c:_0="2" c:_1="PYTHON"/>
                <bean class="com.aruba.bean.Skill" c:_0="3" c:_1="GO"/>
            </array>
        </property>
    </bean>

也可以注入外部引用：

    <bean id="skill1" class="com.aruba.bean.Skill" c:_0="1" c:_1="JAVA"/>
    <bean id="skill2" class="com.aruba.bean.Skill" c:_0="2" c:_1="PYTHON"/>
    <bean id="skill3" class="com.aruba.bean.Skill" c:_0="3" c:_1="GO"/>

    <bean id="user9" class="com.aruba.bean.User" p:username="王五" p:uid="7" p:password="789456">
        <property name="skills2">
            <array>
                <ref bean="skill1"/>
                <ref bean="skill2"/>
                <ref bean="skill3"/>
            </array>
        </property>
    </bean>

2. list集合注入

使用list标签：

    <bean id="user9" class="com.aruba.bean.User" p:username="王五" p:uid="7" p:password="789456">
        <property name="skillList">
            <list>
                <bean class="com.aruba.bean.Skill" c:_0="1" c:_1="JAVA"/>
                <bean class="com.aruba.bean.Skill" c:_0="2" c:_1="PYTHON"/>
                <bean class="com.aruba.bean.Skill" c:_0="3" c:_1="GO"/>
            </list>
        </property>
    </bean>

其他用法和array相同

3. set集合注入

    <bean id="user9" class="com.aruba.bean.User" p:username="王五" p:uid="7" p:password="789456">
        <property name="skillList">
            <set>
                <bean class="com.aruba.bean.Skill" c:_0="1" c:_1="JAVA"/>
                <bean class="com.aruba.bean.Skill" c:_0="2" c:_1="PYTHON"/>
                <bean class="com.aruba.bean.Skill" c:_0="3" c:_1="GO"/>
            </set>
        </property>
    </bean>

4. map注入

    <bean id="user9" class="com.aruba.bean.User" p:username="王五" p:uid="7" p:password="789456">
        <property name="skillMap">
            <map>
                <entry key="JAVA" value-ref="skill1"/>
                <entry key="PYTHON" value-ref="skill2"/>
                <entry key="GO" value-ref="skill3"/>
            </map>
        </property>
    </bean>

5. 定义外部list集合

引入util命名空间：

定义外部list并使用

    <util:list id="sklist">
        <bean id="skill1" class="com.aruba.bean.Skill" c:_0="1" c:_1="JAVA"/>
        <bean id="skill2" class="com.aruba.bean.Skill" c:_0="2" c:_1="PYTHON"/>
        <bean id="skill3" class="com.aruba.bean.Skill" c:_0="3" c:_1="GO"/>
    </util:list>

    <bean id="user9" class="com.aruba.bean.User" p:username="王五" p:uid="7" p:password="789456">
        <property name="skillList" ref="sklist"></property>
    </bean>

六、自定义工厂

新建Java工厂类，实现FactoryBean接口：

public class JobFactory implements FactoryBean<Job> {
    @Override
    public Job getObject() throws Exception {
        Job job = new Job(5, "MANAGER", "MANAGER");
        return job;
    }

    @Override
    public Class<?> getObjectType() {
        return null;
    }
}

xml中配置bean：

    <bean id="job10" class="com.aruba.factory.JobFactory"/>

java中通过容器获取：

    @org.junit.Test
    public void test1() {
        Job job = applicationContext.getBean("job10", Job.class);
        System.out.println(job);
    }

这边是直接获取的Job对象，并不是JobFactory

Spring的xml方式实现di就到此结束了

项目地址：

https://gitee.com/aruba/spring-study.git