一篇文章带你了解Java Spring基础与IOC

目录

• About Spring
• About IOC
• Hello Spring
  • Hello.java
  • Beans.xml
  • Test.java
• IOC创建对象的几种方式
• Spring import settings
• Dependency Injection
  • 1.构造器注入
  • 2.set注入
  • 3.拓展注入
• P-namespcae&C-namespace
• Bean scopes
• singleton
• prototype
• Bean的自动装配
  • byName autowire
  • byType autowire
• 小结

<!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webmvc</artifactId>
    <version>5.3.9</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-jdbc</artifactId>
    <version>5.3.9</version>
</dependency>

private UserDao userDao = null;

public UserServiceImpl(){
    userDao = new UserDaoImpl();
}

userDao = new UserDaoImpls();

public void setUserDao(UserDao userDao) {
    this.userDao = userDao;
}

package com.zh1z3ven.pojo;

public class Hello {
    private String str;

    public Hello() {
    }

    public Hello(String str) {
        this.str = str;
    }

    public String getStr() {
        return str;
    }

    public void setStr(String str) {
        this.str = str;
    }

    @Override
    public String toString() {
        return "Hello{" +
                "str="" + str + """ +
                "}";
    }
}

<?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">
<!--使用Spring创建对象，Spring都称之为bean-->
<!--    一个bean标签代表一个对象， id代表要实例化的对象的名字， class指定这个实体类-->
    <bean id="hello" class="com.zh1z3ven.pojo.Hello">
<!--        设置实体类的属性值-->
        <property name="str" value="Spring"/>
    </bean>
</beans>

public class MyTest {
    public static void main(String[] args) {

        //获取Spring上下文对象
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        //从Spring中取出对象
        Hello hello = (Hello) context.getBean("hello");
        System.out.println(hello);

    }
}

<!--通过下标赋值-->
<bean id="hello2" class="com.zh1z3ven.pojo.Hello">
    <constructor-arg index="0" value="Spring2"/>
</bean>

<!--通过类型赋值-->
<bean id="hello3" class="com.zh1z3ven.pojo.Hello">
    <constructor-arg type="java.lang.String" value="Spring3"/>
</bean>

<!--属性名赋值-->
<bean id="hello4" class="com.zh1z3ven.pojo.Hello">
    <constructor-arg name="str" value="Spring4"/>
</bean>

<!--通过下标赋值-->
<bean id="hello2" class="com.zh1z3ven.pojo.Hello">
    <constructor-arg index="0" value="Spring2"/>
</bean>

<!--通过类型赋值-->
<bean id="hello3" class="com.zh1z3ven.pojo.Hello">
    <constructor-arg type="java.lang.String" value="Spring3"/>
</bean>

<!--属性名赋值-->
<bean id="hello4" class="com.zh1z3ven.pojo.Hello">
    <constructor-arg name="str" value="Spring4"/>
</bean>

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 String apache;
    private Properties info;

    public String getApache() {
        return apache;
    }

    public void setApache(String apache) {
        this.apache = apache;
    }

    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;
    }

    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;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name="" + name + """ +
                ", address=" + address +
                ", books=" + Arrays.toString(books) +
                ", hobbys=" + hobbys +
                ", card=" + card +
                ", games=" + games +
                ", wife="" + wife + """ +
                ", info=" + info +
                "}";
    }
}

<bean id="address" class="com.zh1z3ven.pojo.Address">
    <property name="address" value="beijing"/>
</bean>
<bean id="student1" class="com.zh1z3ven.pojo.Student">
<!--        普通属性值注入-->
    <property name="name" value="zh1z3ven"/>

<!--        ref 引用对象注入-->
    <property name="address" ref="address"/>

<!--        数组array注入-->
    <property name="books">
        <array>
            <value>红楼梦</value>
            <value>西游记</value>
            <value>水浒传</value>
            <value>三国演义</value>
        </array>
    </property>

<!--        List注入-->
    <property name="hobbys">
        <list>
            <value>听音乐</value>
            <value>看电影</value>
            <value>敲代码</value>
            <value>写文章</value>
        </list>
    </property>

<!--        Map注入-->
    <property name="card">
        <map>
            <entry key="银行卡" value="1"></entry>
            <entry key="身份证" value="2"></entry>
            <entry key="学生证" value="3"></entry>
            <entry key="电话卡" value="4"></entry>
            <entry key="校园卡" value="5"></entry>
        </map>
    </property>

<!--        Set注入-->
    <property name="games">
        <set>
            <value>LOL</value>
            <value>CF</value>
            <value>qq</value>
        </set>
    </property>

<!--        null注入-->
    <property name="wife">
        <null></null>
    </property>

<!--        空值注入-->
    <property name="apache" value=""/>

<!--        properties-->
    <property name="info">
        <props>
            <prop key="id">10</prop>
            <prop key="city">北京</prop>
        </props>
    </property>
</bean>

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

<bean id="user1" class="com.zh1z3ven.pojo.User" p:name="zh1z3ven1" p:age="18"/>

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

<bean id="user2" class="com.zh1z3ven.pojo.User" c:name="zh1z3ven2" p:age="19"/>

@Test
public void test(){
    ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
    User user1 = context.getBean("user1", User.class);
    System.out.println(user1.getName());
    System.out.println(user1.getAge());

    User user2 = context.getBean("user2", User.class);
    System.out.println(user2.getName());
    System.out.println(user2.getAge());
}

<bean id="user2" class="com.zh1z3ven.pojo.User" c:name="zh1z3ven2" c:age="19"/>

@Test
public void test(){
    ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
    User user1 = context.getBean("user2", User.class);
    User user2 = context.getBean("user2", User.class);
    System.out.println(user1==user2);
}

public void test2(){
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        User user1 = context.getBean("user2", User.class);
        User user2 = context.getBean("user2", User.class);
        System.out.println(user1==user2);
    }

<bean id="people" class="com.zh1z3ven.pojo.People" autowire="byType">
    <property name="name" value="zh1z3ven"/>
</bean>

<?xml version="1.0" encoding="UTF-8"?>
<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>

public class People {
    @Autowired
    private Cat cat;
    @Autowired
    private Dog dog;
    private String name;

@Autowired
@Qualifier(value="dog222")

javax.annotation.Resource
@Resource //不指定名称自动装配
@Resource(name="") //指定名称自动装配

//相当于在bean中注册,相当于在Spring IoC容器new一个对象
@Component
public class User {
    @Value("CoLoo")
    public String name;

    public String getName() {
        return name;
    }

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

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

@Configuration
@ComponentScan("com.zh1z3ven.pojo")
public class AppConfig {
    @Bean
    public User getUser(){
        return new User();
    }
}

public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
        User user = context.getBean("user", User.class);
        System.out.println(user.getName());
    }
}