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Java学习路线-56:Spring与Ioc

发布时间:2021-11-26 点击数:181

Spring

官网:https://spring.io/

理念:使现有技术更加实用,本身是大杂烩整合现a有的框架技术

优点:

  1. 轻量级框架
  2. Ioc 容器-控制反转 inversion of Control
  3. Aop 面向切面编程
  4. 对事务支持
  5. 对框架的支持

一、Ioc 控制反转

Ioc 是一种编程思想,由主动编程变为被动接收

别名:依赖注入 dependency injection

控制:

指谁来控制对象的创建

传统的应用程序对象的创建是由程序本身控制的

使用 spring 之后,由 spring 创建对象


反转:

正转指程序来创建对象

反转指程序本身不创建对象,而变成被动接受对象


总结:

以前对象是由程序本身创建,

使用 spring 之后,程序变为接收 spring 创建好的对象

简单示例

1、依赖 pom.xml

<dependency>  <groupId>org.springframework</groupId>  <artifactId>spring-context-support</artifactId>  <version>5.2.6.RELEASE</version> </dependency> <dependency>  <groupId>org.springframework</groupId>  <artifactId>spring-context</artifactId>  <version>5.2.6.RELEASE</version> </dependency> 

2、Person.java

package com.pengshiyu.bean;  public class Person {  private String name;    public void setName(String name) {  this.name = name;  }    public void sayHello() {  System.out.println("hello " + this.name);  } } 

3、beans.xml

此处是完整写法,之后将采用简写形式

<?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 name="person" class="com.pengshiyu.bean.Person">  <property name="name" value="张三" />  </bean> </beans> 

4、Demo.java

package com.pengshiyu.spring;  import com.pengshiyu.bean.Person; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext;  public class Demo {  public static void main(String[] args) {  // 解析beans.xml 文件,生成对应的Bean对象  ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");  Person person = (Person)context.getBean("person");  person.sayHello();  } } 

二、Dao 管理示例

Ioc: 对象由 spring 来创建

1、UserDao

package com.spring.dao;  public interface UserDao {  public void getUser(); } 

2、UserDaoMysqlImpl

package com.spring.dao.impl;  import com.spring.dao.UserDao;  public class UserDaoMysqlImpl implements UserDao {  @Override  public void getUser() {  System.out.println("Mysql 获取用户信息");  } } 

3、UserDaoOracleImpl

package com.spring.dao.impl;  import com.spring.dao.UserDao;  public class UserDaoOracleImpl implements UserDao {  @Override  public void getUser() {  System.out.println("Oracle 获取用户信息");  } } 

4、UserService

package com.spring.service;  public interface UserService {  public void getUser(); } 

5、UserServiceImpl

package com.spring.service.impl;  import com.spring.dao.UserDao; import com.spring.service.UserService;  public class UserServiceImpl implements UserService {   private UserDao userDao = null;   public void setUserDao(UserDao userDao) {  this.userDao = userDao;  }   @Override  public void getUser() {  this.userDao.getUser();  } } 

6、beans.xml(简化版)

 <beans >  <bean id="mysqlDao" class="com.spring.dao.impl.UserDaoMysqlImpl" />  <bean id="oracleDao" class="com.spring.dao.impl.UserDaoOracleImpl" />  <bean id="service" class="com.spring.service.impl.UserServiceImpl">  <property name="userDao" ref="mysqlDao"></property>  </bean>  </beans> 

7、TestDemo

package com.spring.test;  import com.spring.service.UserService; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext;  public class TestDemo {  public static void main(String[] args) {  ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");  UserService service = (UserService)context.getBean("service");  service.getUser();  } } 

三、使用 Ioc 来创建对象的 3 种方法

Person 类

package com.pengshiyu.bean;  public class Person {   private String name;   public Person() {   }   public Person(String name) {  this.name = name;  }   public void sayHello() {  System.out.println("hello " + this.name);  } }

创建对象

package com.spring.test;   import com.pengshiyu.bean.Person; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext;  public class Demo {  public static void main(String[] args) {  ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");  Person person = (Person) context.getBean("person");  person.sayHello();   } } 

beans.xml(简化版)

1、无参构造

<beans>  <bean name="person" class="com.pengshiyu.bean.Person" /> </beans>

2、有参构造

(1)根据参数下标设置

<beans>  <bean name="person" class="com.pengshiyu.bean.Person">  <!-- index 构造方法下标从 0 开始 -->  <constructor-arg index="0" value="Tom" />  </bean> </beans>

(2)根据参数名称设置

<beans>  <bean name="person" class="com.pengshiyu.bean.Person">  <!-- name 参数名-->  <constructor-arg name="name" value="Tom" />  </bean> </beans>

3、工厂方法创建

(1)静态工厂

package com.pengshiyu.factory;  import com.pengshiyu.bean.Person;  public class PersonFactory {  public static Person newInstance(String name) {  return new Person(name);  } } 
<beans >  <bean name="person" class="com.pengshiyu.factory.PersonFactory" factory-method="newInstance">  <constructor-arg name="name" value="Tom" />  </bean>  </beans> 

(2)动态工厂

package com.pengshiyu.factory;  import com.pengshiyu.bean.Person;  public class PersonFactory {  public Person newInstance(String name) {  return new Person(name);  } } 
<beans>   <bean id="factory" class="com.pengshiyu.factory.PersonFactory" />   <bean name="person" factory-bean="factory" factory-method="newInstance">  <constructor-arg name="name" value="Tom"/>  </bean>  </beans> 

注意静态工厂static

四、Spring 配置文件

id 是 bean 的唯一标识符,如果没有配置 id,name 默认为标识符

如果配置了 id,又配置了 name,则 name 是别名

name 可以设置多个别名分隔符可以是空格、逗号、分号

class 是 bean 的全限定名=包名+类名

如果不配置 id 和 name,那么可以可以使用如下方式获取对象

applicationContext.getBean(class)

配置如下

<beans >  <bean id="person1" name="person user" class="com.pengshiyu.bean.Person" /> </beans>

获取方式

Person person = (Person) context.getBean("person1");  // 或者 Person person = (Person) context.getBean("user");  // 或者 Person person = (Person) context.getBean(Person.class);

导入文件

<beans>  <import resource="person.xml"/> </beans>

五、Spring 依赖注入 DI

dependency injection

依赖:指 bean 对象创建依赖于容器,bean 对象的依赖资源

注入:指 bean 对象依赖的资源由容器来设置和装配

spring 注入

测试

package com.spring.test;   import com.pengshiyu.bean.Person; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext;  public class Demo {  public static void main(String[] args) {  ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");  Person person = (Person) context.getBean("person");  person.sayHello();   } } 
  1. 构造器注入
package com.pengshiyu.bean;  public class Person {   private String name;   public Person(String name) {  this.name = name;  }   public void sayHello() {  System.out.println("hello " + this.name);  } } 
<beans>  <bean name="person" class="com.pengshiyu.bean.Person">  <constructor-arg name="name" value="Tom"/>  </bean> </beans>
  1. setter 注入

(1)常量注入

package com.pengshiyu.bean;  public class Person {   private String name;   public void setName(String name) {  this.name = name;  }   public void sayHello() {  System.out.println("hello " + this.name);  } } 
<beans >  <bean name="person" class="com.pengshiyu.bean.Person">  <property name="name" value="Tom"/>  </bean> </beans> 

(2)bean 注入

package com.pengshiyu.bean;  public class Address {  private String address;   public void setAddress(String address) {  this.address = address;  }   public String getAddress() {  return address;  } } 
package com.pengshiyu.bean;  public class Person {   private String name;  private Address address;   public void setAddress(Address address) {  this.address = address;  }   public void setName(String name) {  this.name = name;  }   public void sayHello() {  System.out.println("hello " + this.name + this.address.getAddress());  } } 
<beans >   <bean id="address" class="com.pengshiyu.bean.Address">  <property name="address" value="北京"/>  </bean>   <bean name="person" class="com.pengshiyu.bean.Person">  <property name="name" value="Tom"/>  <property name="address" ref="address"/>  </bean>  </beans> 

(3)数组注入

package com.pengshiyu.bean;  public class Book {  private  String name;   public Book(String name){  this.name = name;  }   @Override  public String toString() {  return "《" + this.name + "》";  } } 
package com.pengshiyu.bean;  import java.util.Arrays;  public class Person {   private Book[] books;   public void setBooks(Book[] books) {  this.books = books;  }   @Override  public String toString() {  return "Person{" +  "books=" + Arrays.toString(books) +  '}';  } } 
<beans >  <bean name="person" class="com.pengshiyu.bean.Person">  <property name="books">  <array>  <value>水浒传</value>  <value>红楼梦</value>  <value>三国演义</value>  <value>西游记</value>  </array>  </property>  </bean> </beans>

(4)List 注入

package com.pengshiyu.bean;  import java.util.Arrays; import java.util.List;  public class Person {   private List<String>[] books;   public void setBooks(List<String>[] books) {  this.books = books;  }   @Override  public String toString() {  return "Person{" +  "books=" + Arrays.toString(books) +  '}';  } } 
<beans>  <bean name="person" class="com.pengshiyu.bean.Person">  <property name="books">  <list>  <value>水浒传</value>  <value>红楼梦</value>  <value>三国演义</value>  <value>西游记</value>  </list>  </property>  </bean> </beans>

(5)Map 注入

package com.pengshiyu.bean;  import java.util.Map;  public class Person {   private Map<String, String> cards;   public void setCards(Map<String, String> cards) {  this.cards = cards;  }   @Override  public String toString() {  return cards.toString();  } } 
<beans>  <bean name="person" class="com.pengshiyu.bean.Person">  <property name="cards">  <map>  <entry key="中国银行" value="123456"></entry>  <entry key="建设银行" value="123456"></entry>  </map>  </property>  </bean> </beans>

(6)Set 注入

package com.pengshiyu.bean;  import java.util.Set;  public class Person {   private Set<String> games;   public void setGames(Set<String> games) {  this.games = games;  }   @Override  public String toString() {  return games.toString();  } } 
<beans>  <bean name="person" class="com.pengshiyu.bean.Person">  <property name="games">  <set>  <value>英雄联盟</value>  <value>王者荣耀</value>  </set>  </property>  </bean> </beans> 

(7)null 注入

package com.pengshiyu.bean;  public class Person {   public void setWife(String wife) {  this.wife = wife;  }   private String wife;   @Override  public String toString() {  return wife;  } } 
<beans>  <bean name="person" class="com.pengshiyu.bean.Person">  <property name="wife"><null/></property>  </bean> </beans>

(8) Properties 注入

package com.pengshiyu.bean;  import java.util.Properties;  public class Person {  private Properties props;   public void setProps(Properties props) {  this.props = props;  }   @Override  public String toString() {  return this.props.toString();  } } 
 <beans >  <bean name="person" class="com.pengshiyu.bean.Person">  <property name="props">  <props>  <prop key="name">Tom</prop>  <prop key="sex">Man</prop>  </props>  </property>  </bean> </beans> 

(9) p 命名空间注入

需要有对应的 set 方法

package com.pengshiyu.bean;  public class Person {  private String name;  private int age;   public void setName(String name) {  this.name = name;  }   public void setAge(int age) {  this.age = age;  }   @Override  public String toString() {  return "Person{" +  "name='" + name + '\'' +  ", age=" + age +  '}';  } } 

头文件需要引入

xmlns:p="http://www.springframework.org/schema/p"
<?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:p="http://www.springframework.org/schema/p"  xsi:schemaLocation="http://www.springframework.org/schema/beans  http://www.springframework.org/schema/beans/spring-beans.xsd">   <bean name="person" class="com.pengshiyu.bean.Person"  p:name="Tom" p:age="23"/> </beans> 

(10)c 命名空间注入

要求有对应的构造方法

package com.pengshiyu.bean;  public class Person {  private String name;  private int age;   public Person(String name, int age) {  this.name = name;  this.age = age;  }   @Override  public String toString() {  return "Person{" +  "name='" + name + '\'' +  ", age=" + age +  '}';  } } 

头文件需要引入

xmlns:c="http://www.springframework.org/schema/c"
<?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:c="http://www.springframework.org/schema/c"  xsi:schemaLocation="http://www.springframework.org/schema/beans  http://www.springframework.org/schema/beans/spring-beans.xsd">   <bean name="person" class="com.pengshiyu.bean.Person"  c:name="Tom" c:age="23"/> </beans> 

六、bean 的作用域

spring

桥梁 轻量级 易学 ioc di app 事务 整合框架

scope:

  1. singleton 单例 整个容器只有一个对象实例(默认)
  2. prototype 原型 每次获取 Bean 都产生一个新对象
  3. request 每次请求时创建一个新的对象
  4. session 会话范围内有一个对象
  5. global session 只在 portlet 下有用,表示 applicatio
  6. application 在应用范围中有一个对象


Bean 自动装配

autowire

  1. byName
  2. byType
  3. constructor

不推荐使用自动装配