Spring学习笔记（二）

三、依赖注入

3.1构造器注入

3.2 Set方式注入

student.java

package pojo;

import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

public class Student {
    private String name;
    private String[] subject;
    private List<String> hobbys;
    private Map<String,Integer> score;
    private Set<String> teacher;
    private Properties properties;
    private Address address;
    private String grilfriend;

    @Override
    public String toString() {
        return "{name:  " + this.name +
                ",\n subject: " + this.subject +
                ",\n hobbys: " + this.hobbys +
                ",\n score: " + this.score +
                ",\n teacher: " + this.teacher +
                ",\n properties: " + this.properties +
                ",\n address" + this.address.getAddress();
    }

    public String getName() {
        return name;
    }

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

    public String[] getSubject() {
        return subject;
    }

    public void setSubject(String[] subject) {
        this.subject = subject;
    }

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

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

    public Map<String, Integer> getScore() {
        return score;
    }

    public void setScore(Map<String, Integer> score) {
        this.score = score;
    }

    public Set<String> getTeacher() {
        return teacher;
    }

    public void setTeacher(Set<String> teacher) {
        this.teacher = teacher;
    }

    public Properties getProperties() {
        return properties;
    }

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

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    public void setGrilfriend(String grilfriend) {
        this.grilfriend = grilfriend;
    }
}

Address.java

package pojo;

public class Address {
    private String address;

    public Address(String address) {
        this.address = address;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

beans.xml

<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="pojo.Address">
        <constructor-arg index="0" value="河北省保定市"/>
    bean>

    <bean id="student" class="pojo.Student">
        <property name="name" value="小明"/>

        
        <property name="address" ref="address"/>

        
        <property name="subject">
            <array>
                <value>数学value>
                <value>语文value>
                <value>英语value>
            array>
        property>
        
        <property name="hobbys">
            <list>
                <value>学习value>
                <value>打篮球value>
                <value>看电视value>
            list>
        property>

        
        <property name="score">
            <map>
                <entry key="语文" value="111"/>
                <entry key="数学" value="100"/>
                <entry key="英语" value="99"/>
            map>
        property>

        

        <property name="teacher">
            <set>
                <value>老张value>
                <value>老刘value>
            set>
        property>

        
        <property name="properties">
            <props>
                <prop key="学号">123456prop>
                <prop key="学院编号">11111prop>
            props>
        property>

        
        <property name="grilfriend">
            <null>null>
        property>
    bean>
beans>

测试

public class StudentTest {

    @Test
    public void test(){
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");

        Object student = context.getBean("student");
        System.out.println(student);
    }
}

3.3 扩展方式注入

3.3.1 P命名空间

p命名空间对应

引入

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

使用

<bean id="user" class="pojo.User" p:name="xxx" p:age="10"/>

3.3.2 C命名空间

c命名空间对应 实体类必须有相应的构造方法才能使用

引入

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

使用

<bean id="user1" class="pojo.User" c:name="yyy" c:age="18"/>
<bean id="user2" class="pojo.User" c:_0="qqq" c:_1="10"/>

3.4 bean的作用域

• 单例模式

  默认是单例模式，也可手动设置，每次调用生成的都是同一个对象

  <bean id="user" class="pojo.User" p:name="xxx" p:age="10" scope="singleton"/>
  

• 原型模式

  每次调用都会生成一个新的对象

  <bean id="user" class="pojo.User" p:name="xxx" p:age="10" scope="prototype"/>
  

四、Bean的自动装配

User类

package pojo;

public class User {


    private Dog dog;
    private Car car;

    @Override
    public String toString() {
        return dog.getName() + "\n" + car.getName();
    }

    public Dog getDog() {
        return dog;
    }

    public void setDog(Dog dog) {
        this.dog = dog;
    }

    public Car getCar() {
        return car;
    }

    public void setCar(Car car) {
        this.car = car;
    }
}

Car类

package pojo;

public class Car {
    private String name;

    public Car(){
    }

    public String getName() {
        return name;
    }

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

Dog类

package pojo;

public class Dog {
    private String name;

    public Dog() {
    }

    public String getName() {
        return name;
    }

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

4.4.1 byName自动装配

byName自动装配，要求所有bean的id唯一，byName会自动在容器上下文中寻找，和自己对象Set方法参数名对应的bean id

<bean id="car" class="pojo.Car" p:name="dididi" />
<bean id="dog" class="pojo.Dog" p:name="wangwangwang"/>

<bean id="user" class="pojo.User" autowire="byName"/>

测试

4.4.2 byType自动装配

要求所有bean的class唯一，byType会自动在容器上下文中寻找和自己对象属性类型相同的bean

    <bean id="car123" class="pojo.Car" p:name="dididi" />
    <bean id="dog111" class="pojo.Dog" p:name="wangwangwang"/>


    <bean id="user" class="pojo.User" autowire="byType"/>

4.4.3 注解实现自动装配

配置

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        https://www.springframework.org/schema/context/spring-context.xsd">

    <context:annotation-config/>

beans>

@Autowired

通过byType实现

直接在成员变量上使用

@Autowired
private Dog dog;
@Autowired
private Car car;

也可在Set方法上使用

@Autowired
    public void setDog(Dog dog) {
        this.dog = dog;
    }

    @Autowired
    public void setCar(Car car) {
        this.car = car;
    }

二者可以混合使用

//如果定义了required的属性为false，说明这个对象可以为null，否则不需为空
@Autowired(required = false)

等同于@Nullable，字段加了这个注解，说明这个字段可以为null

@Qualifier

指定相应的bean

<bean id="car123" class="pojo.Car" p:name="didi" />
<bean id="car222" class="pojo.Car" p:name="dididi" />
<bean id="dog111" class="pojo.Dog" p:name="wangwang"/>
<bean id="dog222" class="pojo.Dog" p:name="wangwang"/>

    @Autowired
    @Qualifier(value = "dog111")
    private Dog dog;

    @Autowired
    @Qualifier(value = "car123")
    private Car car;

@Resource

@Resource(name = "dog111")
private Dog dog;

@Resource
private Car car;

会先根据名字去查找有没有对应的class，如果没有会去查找有没有相应的id，如果都没有才会报错

Resource也可以指定id

五、使用注解开发

    
    <context:component-scan base-package="pojo"/>
    <context:annotation-config/>

@Component

//等价于
@Component
public class User {
    private String name;
}

@Value

public class User {

    //等价于
    @Value("xiaoming")
    private String name;
}

@Scope

@Component
@Scope("singleton")
public class User {

    //等价于
    @Value("xiaoming")
    private String name;
}

衍生的注解

@Component有几个衍生的注解，我们在web开发中，会按照mvc三层架构分才能

• dao （@Repository)
• service (@Service)
• controller (@Controller)