spring学习二：DI与IOC

最新推荐文章于 2024-12-25 09:00:00 发布

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最新推荐文章于 2024-12-25 09:00:00 发布

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分类专栏： spring

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IoC：Inversion of control：控制反转：在传统开发模式下，对象的创建过程和管理过程都是由开发者通过Java程序来实现的，操作权在开发者的Java程序中，当使用了Spring框架后，对象的创建与管理都不再由开发者编写的程序来决定！而是交给框架来决定，具体的做法可以是通过配置框架的XML文件来实现，或其它方式。

DI：Dependency Injection：依赖注入：为类的属性注入值。

IoC是Spring框架所实现的目标，而DI是实现该目标所使用的手段，即：Spring通过DI实现了IoC。

1、注入已有对象：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns="http://www.springframework.org/schema/beans"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd">

    <!--
    bean:被容器所管理的对象
		bean标签有两个必要属性：
		id:bean的名称，要求唯一，不能冲突
		class:要写的类的完整的名字(包名.类名)
		注:Spring容器是利用java反射来查找类的字节码文件，然后完成类的加载
		Map<String, Object> map = new HashMap<String, Object>();
		Class<?> c = Class.forName("first.Apple");
		Object a1 = c.newInstance();
		map.put("a1", a1);
    -->

    <!--通过默认空参构造创建bean-->
    <bean id="object" class="java.lang.Object"/>

    <!--
    通过静态工厂方法创建bean
    Calendar c = Calendar.getInstance();
    factory-method:用来指定一个静态工厂方法。
    注:容器会调用该方法来创建对象
    -->
    <bean id="calendar" class="java.util.Calendar" factory-method="getInstance"/>

    <!-- 利用实例工厂方法来创建对象 -->
    <!--
        factory-bean:指定一个bean的id(其实就是指定一个对象)。
        容器会调用该bean的实例方法来创建对象。
     -->
    <bean id="date1" factory-bean="calendar" factory-method="getTime"/>
</beans>

public class TestCase {

    private AbstractApplicationContext app;

    @Before
    public void before() {
        app = new ClassPathXmlApplicationContext("classpath:spring.xml");
    }

    @After
    public void after() {
        app.close();
    }

    @Test
    public void test() {
        Object obj = app.getBean("object", Object.class);
        System.out.println(obj);
        Object calendar = app.getBean("calendar", Calendar.class);
        System.out.println(calendar);
        Object date = app.getBean("date", Date.class);
        System.out.println(date);
    }
}

2、注入自定义对象：

1）使用set注入，其实set注入就是通过调用set方法注入的。

public class User {
    private String name;
    private int age;
    private String[] arrString;
    private int[] arrInt;
    private Integer[] arrInteger;
    private Set<String> set;
    private Map<String, Object> map;
    private List<String> list;
    private Properties prop;
    private Date date;
    private Calendar cal;

    public void setName(String name) {
        this.name = name;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public void setArrString(String[] arrString) {
        this.arrString = arrString;
    }

    public void setArrInt(int[] arrInt) {
        this.arrInt = arrInt;
    }

    public void setArrInteger(Integer[] arrInteger) {
        this.arrInteger = arrInteger;
    }

    public void setSet(Set<String> set) {
        this.set = set;
    }

    public void setMap(Map<String, Object> map) {
        this.map = map;
    }

    public void setList(List<String> list) {
        this.list = list;
    }

    public void setProp(Properties prop) {
        this.prop = prop;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public void setCal(Calendar cal) {
        this.cal = cal;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", arrString=" + Arrays.toString(arrString) +
                ", arrInt=" + Arrays.toString(arrInt) +
                ", arrInteger=" + Arrays.toString(arrInteger) +
                ", set=" + set +
                ", map=" + map +
                ", list=" + list +
                ", prop=" + prop +
                ", date=" + date +
                ", cal=" + cal +
                '}';
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns="http://www.springframework.org/schema/beans"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd">

    <bean id="calendar" class="java.util.Calendar" factory-method="getInstance"/>

    <bean id="date" factory-bean="calendar" factory-method="getTime"/>

    <bean id="user" class="org.spring.teach.User">
        <!--基本类型(包含String)-->
        <property name="name" value="zhangsan"/>
        <property name="age" value="23"/>
        <property name="arrInt">
            <!-- 数组类型 -->
            <array>
                <value>1</value>
                <value>2</value>
                <value>3</value>
                <value>4</value>
            </array>
        </property>
        <property name="arrString">
            <array>
                <value>1</value>
                <value>2</value>
                <value>3</value>
                <value>4</value>
                <value>hello</value>
            </array>
        </property>
        <property name="arrInteger">
            <!-- 数组类型也可以使用list注入 -->
            <list>
                <value>1</value>
                <value>2</value>
                <value>3</value>
                <value>4</value>
            </list>
        </property>
        <property name="map">
            <!-- map类型 -->
            <map>
                <entry key="id" value="1"/>
                <entry key="name" value="zhangsan"/>
                <entry key="age" value="23"/>
                <entry key="date" value-ref="date"/>
            </map>
        </property>
        <property name="set">
            <!-- set类型 -->
            <set>
                <value>zhangsan</value>
                <value>lisi</value>
                <value>wangwu</value>
                <value>zhaoliu</value>
            </set>
        </property>
        <property name="list">
            <!-- list类型 -->
            <list>
                <value>1</value>
                <value>2</value>
                <value>3</value>
                <value>4</value>
                <value>hello</value>
            </list>
        </property>
        <property name="prop">
            <!--properties类型-->
            <props>
                <prop key="name">zhangsan</prop>
                <prop key="age">age</prop>
                <prop key="gender">gender</prop>
            </props>
        </property>
        <!-- 引用类型 -->
        <property name="cal" ref="calendar"/>
        <property name="date" ref="date"/>
    </bean>
</beans>

public class TestCase {

    private AbstractApplicationContext app;

    @Before
    public void before() {
        app = new ClassPathXmlApplicationContext("classpath:spring.xml");
    }

    @After
    public void after() {
        app.close();
    }

    @Test
    public void test() {
        User user = app.getBean("user", User.class);
        System.out.println(user);
    }
}

一月 24, 2019 10:55:13 下午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@9e89d68: startup date [Thu Jan 24 22:55:13 CST 2019]; root of context hierarchy
一月 24, 2019 10:55:13 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [spring.xml]
User{name='zhangsan', age=23, arrString=[1, 2, 3, 4, hello], arrInt=[1, 2, 3, 4], arrInteger=[1, 2, 3, 4], set=[zhangsan, lisi, wangwu, zhaoliu], map={id=1, name=zhangsan, age=23, date=Thu Jan 24 22:55:14 CST 2019}, list=[1, 2, 3, 4, hello], prop={user=c##root, url=jdbc:oracle:thin:@localhost:1521:orcl, driver=oracle.jdbc.driver.OracleDriver, initSize=1, pwd=c##root, maxSize=3}, date=Thu Jan 24 22:55:14 CST 2019, cal=java.util.GregorianCalendar[time=1548341714228,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Shanghai",offset=28800000,dstSavings=0,useDaylight=false,transitions=19,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2019,MONTH=0,WEEK_OF_YEAR=4,WEEK_OF_MONTH=4,DAY_OF_MONTH=24,DAY_OF_YEAR=24,DAY_OF_WEEK=5,DAY_OF_WEEK_IN_MONTH=4,AM_PM=1,HOUR=10,HOUR_OF_DAY=22,MINUTE=55,SECOND=14,MILLISECOND=228,ZONE_OFFSET=28800000,DST_OFFSET=0]}
一月 24, 2019 10:55:14 下午 org.springframework.context.support.ClassPathXmlApplicationContext doClose

信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@9e89d68: startup date [Thu Jan 24 22:55:13 CST 2019]; root of context hierarchy

Process finished with exit code 0

2）构造方法注入

public class User {
    private Phone phone;


    public User(Phone phone) {
        this.phone = phone;
    }

    @Override
    public String toString() {
        return "User{" +
                "phone=" + phone +
                '}';
    }
}

public class Phone {
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns="http://www.springframework.org/schema/beans"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd
                            http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.3.xsd">

    <bean id="phone" class="org.spring.teach.Phone"/>
    <bean id="user" class="org.spring.teach.User">
        <!-- index表示构造器中的参数顺序,从0开始 -->
        <constructor-arg index="0" ref="phone"/>
    </bean>
</beans>

public class TestCase {

    private AbstractApplicationContext app;

    @Before
    public void before() {
        app = new ClassPathXmlApplicationContext("classpath:spring.xml");
    }

    @After
    public void after() {
        app.close();
    }

    @Test
    public void test() {
        User user = app.getBean("user", User.class);
        System.out.println(user);
    }
}

一月 24, 2019 10:59:20 下午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@9e89d68: startup date [Thu Jan 24 22:59:20 CST 2019]; root of context hierarchy
一月 24, 2019 10:59:20 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [spring.xml]
User{phone=org.spring.teach.Phone@5b87ed94}
一月 24, 2019 10:59:21 下午 org.springframework.context.support.ClassPathXmlApplicationContext doClose

信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@9e89d68: startup date [Thu Jan 24 22:59:20 CST 2019]; root of context hierarchy

Process finished with exit code 0