Spring入门之依赖注入（DI）

Spring依赖注入的方式有两种，分别是构造器依赖注入和set方法依赖注入。

---

第一种方式（构造器）：
1.新建Student.java

public class Student {
    public void say(){
        System.out.println("say");
    }
}

2.新建Person.java

public class Person {
    private Long pid;
    private String pname;
    private Student student;

    public Person(Long pid,String pname){
        this.pid = pid;
        this.pname = pname;
    }

    public Person(String pname,Student student){
        this.pname = pname;
        this.student = student;
    }

    public Long getPid() {
        return pid;
    }

    public String getPname() {
        return pname;
    }

    public Student getStudent() {
        return student;
    }
}

3.配置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-2.5.xsd">
    <bean id="person" class="spring.di.xml.constructor.Person">
    <!-- 
        构造函数的参数
            index:第几个参数，下标从0开始
            type：参数的类型
            ref ：如果类型是引用类型，赋值
            value：如果类型是基本类型，赋值
        说明：
            只能指定一个构造函数
     -->
    <constructor-arg index="0" type="java.lang.Long" value="5"></constructor-arg>
    <constructor-arg index="1" type="java.lang.String" value="张三"></constructor-arg>
    <!-- <constructor-arg index="2" type="spring.di.xml.constructor.Student" ref="student"></constructor-arg> -->
    </bean>
    <bean id="student" class="spring.di.xml.constructor.Student"></bean>
</beans>   

4.新建工具类SpringHelper.java

public class SpringHelper {
    public static ApplicationContext context;
    public static String path;
    @Before
    public void startSpring(){
        context = new ClassPathXmlApplicationContext(path);
    }
}

5.新建测试类PersonTest.java

public class PersonTest extends SpringHelper{
    static{
        path = "spring/di/xml/constructor/applicationContext.xml";
    }

    @Test
    public void test(){
        Person person = (Person) context.getBean("person");
        System.out.println(person.getPid());
        System.out.println(person.getPname());
    }
}

---

第二种方式（set方法）：
1.新建Student.java

public class Student {
    public void say(){
        System.out.println("say");
    }
}

2.新建Person.java

public class Person {
    private Long pid;//包装类型
    private String pname;//String类型
    private Student student;//引用类型

    private List lists;

    private Set sets;

    private Map map;

    private Properties properties;

    public Long getPid() {
        return pid;
    }

    public void setPid(Long pid) {
        this.pid = pid;
    }

    public String getPname() {
        return pname;
    }

    public void setPname(String pname) {
        this.pname = pname;
    }

    public Student getStudent() {
        return student;
    }

    public void setStudent(Student student) {
        this.student = student;
    }

    public List getLists() {
        return lists;
    }

    public void setLists(List lists) {
        this.lists = lists;
    }

    public Set getSets() {
        return sets;
    }

    public void setSets(Set sets) {
        this.sets = sets;
    }

    public Map getMap() {
        return map;
    }

    public void setMap(Map map) {
        this.map = map;
    }

    public Properties getProperties() {
        return properties;
    }

    public void setProperties(Properties properties) {
        this.properties = properties;
    }
}

3.配置xml文件：

<?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-2.5.xsd">
    <bean id="person" class="spring.di.xml.set.Person">
        <!-- 
            property:属性(name是根据set方法的)
                在spring中
                    基本类型（包装类型和String类型）都可以用value来赋值
                    引用类型用ref赋值

         -->
        <property name="pid" value="5"></property>
        <property name="pname" value="张三"></property>
        <property name="student">
            <ref bean="student"/>
        </property>
        <property name="lists">
            <list>
                <value>list1</value>
                <value>list2</value>
                <ref bean="student"/>
            </list>
        </property>
        <property name="sets">
            <set>
                <value>set1</value>
                <value>set2</value>
                <ref bean="student"/>
            </set>
        </property>
        <property name="map">
            <map>
                <entry key="map1">
                    <value>map1</value>
                </entry>
                <entry key="map2">
                    <value>map2</value>
                </entry>
                <entry key="map3">
                    <ref bean="student"/>
                </entry>
            </map>
        </property>
        <property name="properties">
            <props>
                <prop key="prop1">
                    prop1
                </prop>
            </props>
        </property>
    </bean>           
    <bean id="student" class="spring.di.xml.set.Student"></bean>
</beans>   

4.新建测试类

public class PersonTest extends SpringHelper{
    static{
        path = "spring/di/xml/set/applicationContext.xml";
    }

    @Test
    public void test(){
        Person person = (Person) context.getBean("person");
        person.getStudent().say();
        System.out.println(person.getPid());
        System.out.println(person.getPname());

        List lists = person.getLists();
        for(int i = 0;i < lists.size();i++){
            System.out.println(lists.get(i).toString());
        }
    }
}