上线了建站怎么收费,wordpress上传图片不显示,网站多个用户怎样建设,网页自我介绍制作模板IOC
1.概述
IOC#xff1a;Inversion of Control 控制反转#xff0c;可以让容器负责对象的创建以及销毁操作#xff0c;对象在容器中叫 bean
2.回顾问题 问题#xff1a;写了太多与业务无关的代码 耦合度非常高#xff0c;写了很多和业务无关的代码不利于项目的升级迭…IOC
1.概述
IOCInversion of Control 控制反转可以让容器负责对象的创建以及销毁操作对象在容器中叫 bean
2.回顾问题 问题写了太多与业务无关的代码 耦合度非常高写了很多和业务无关的代码不利于项目的升级迭代 思考的解决方案 能够直接获取 mapper 接口而不必去关心底层的获取方式
3.bean 配置
3.1.创建 spring01 项目 项目结构如下 添加 Spring 依赖 dependencies
!-- 添加 spring 依赖--dependencygroupIdorg.springframework/groupIdartifactIdspring-context/artifactIdversion5.2.17.RELEASE/version/dependency
!-- 添加 junit 依赖--dependencygroupIdjunit/groupIdartifactIdjunit/artifactIdversion4.12/version
!-- scopetest/scope--/dependency/dependencies3.2.添加 Student 类 创建空学生类 public class Student {
}3.3.添加 Spring 配置文件 添加方式如下 开始配置 javabean ?xml version1.0 encodingUTF-8?
beans xmlnshttp://www.springframework.org/schema/beansxmlns:xsihttp://www.w3.org/2001/XMLSchema-instancexsi:schemaLocationhttp://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
!-- 配置 Student 学生类--bean idstudent namestu classcn.sycoder.domian.Student/bean
/beans4.属性介绍
属性名称说明id给 bean 起名字定义id 不能重复name给 bean 起别名class类全限定类名
4.容器创建
4.1.ClassPathXmlApplicationContext
从classPath下寻找
ApplicationContext context new ClassPathXmlApplicationContext(beans.xml);
System.out.println(context);4.2.FileSystemXmlApplicationContext
从系统文件下寻找
ApplicationContext ctx new FileSystemXmlApplicationContext(绝对路径地址);使用 ClassPathXmlApplicationContext 获取方式会出现如下问题
5.从容器中获取 bean
5.1.根据id 获取
ApplicationContext context new ClassPathXmlApplicationContext(beans.xml);//从容器中根据 id 获取 bean 对象
Student stu (Student)context.getBean(student);//通过别名获取 bean 对象
Student stuByName (Student)context.getBean(stu);注意如果id重复会有如下问题
5.2.根据id和类型
ApplicationContext context new ClassPathXmlApplicationContext(beans.xml);
final Student student context.getBean(student, Student.class);5.3.根据类型获取bean
ApplicationContext context new ClassPathXmlApplicationContext(beans.xml);
final Student bean context.getBean(Student.class);注意使用类型获取的时候一定要保证容器中只有一个 javabean 对象
5.4.注意点 bean 的配置spring 是使用反射调用对象的无参构造器实现的。所以必须提供无参构造器否则会出现如下错误
6.设计模式
6.1.单例模式 概述属于创建型模式提供了创建对象的最佳方式。单例模式只能有一个单一的类 懒汉式单例模式:需要用的时候再去把对象创建出来 public class SingleObject {//线程不安全的懒汉式单例模式private static SingleObject instance;public static SingleObject getInstance(){if(instance null){instance new SingleObject();}return instance;}}饿汉式单例模式不管你有没有我先创建出来 public class SingleObjectE {//线程不安全的饿汉式单例模式private static SingleObjectE instance new SingleObjectE();public static SingleObjectE getInstance(){return instance;}
}6.2.工厂模式 概述也是属于创建型模式目的也是提供创建对象的最佳方式 静态工厂 public class BeanFactory {public static Student getBean() {return new Student();}public static Object getBean(String name) {if (Student.equals(name))return new Student();else if(SingleObject.equals(name)) {return new SingleObject();}else{return new Object();}}}实例工厂 public class BeanFactory {public Object getBean(){return new Student();}
}6.3.通过反射获取 xml 配置创建对象、 模拟实现IOC获取对象 导依赖 dependencygroupIdorg.dom4j/groupIdartifactIddom4j/artifactIdversion2.1.3/version
/dependency
dependencygroupIdjaxen/groupIdartifactIdjaxen/artifactIdversion1.2.0/version
/dependency代码实现 public class XmlCreateBean {/*** 模拟spring 容器创建 javabean* param configName* param id* return*/public static Object getBean(String configName,String id){final SAXReader saxReader new SAXReader();try {final Document dom saxReader.read(configName);final Element element dom.getRootElement();final ListElement beans element.elements(bean);//获取每一个 beanfor (Element bean : beans) {if(id.equals(bean.attributeValue(id))){final String aClass bean.attributeValue(class);final Class? clz Class.forName(aClass);return clz.newInstance();}}} catch (Exception e) {e.printStackTrace();}return null;}
}7. bean实例化
bean 交给 spring 创建底层究竟是怎么创建的实例化 bean 三种方式 构造器(常用)静态工厂方法实例工厂方法实现 FactoryBean常用
1.无参构造器实例化 新建 person 类底层是通过 clz.getDeclaredClasses() 获取构造器 public class Person {public Person(){}}配置 Person bean bean idperson classcn.sycoder.domian.Person/bean从容器中获取 bean Testpublic void testConstructorInit(){final ClassPathXmlApplicationContext context new ClassPathXmlApplicationContext(beans.xml);Person p (Person) context.getBean(person);}修改构造器添加参数测试提示找不到无参构造器
2.静态工厂方法实例化 创建 clintServer 类,提供静态工厂方法 public class ClientServer {//创建自身对象并且私有化private static ClientServer clientServer new ClientServer();private ClientServer() {}public static ClientServer createInstance(){return clientServer;}
}配置bean 的 xml bean idclientServer classcn.sycoder.domian.ClientServer factory-methodcreateInstance/bean获取 bean Testpublic void testFactoryStaticMethodInit(){final ClassPathXmlApplicationContext context new ClassPathXmlApplicationContext(beans.xml);final ClientServer bean context.getBean(ClientServer.class);}配置关系
3.实例工厂方法实例化 创建实例工厂类 public class ClientServiceFactory {private static ClientService instance new ClientService();private ClientServiceFactory(){}public ClientService getInstance(){return instance;}
}public class ClientService {
}配置 bean !-- 配置工厂--bean idclientFactory classcn.sycoder.domian.ClientServiceFactory/bean
!-- 配置 clientService--bean idclientService factory-beanclientFactory factory-methodgetInstance/bean获取bean Testpublic void testFactoryInstanceMethodInit(){final ClassPathXmlApplicationContext context new ClassPathXmlApplicationContext(beans.xml);final ClientService bean context.getBean(ClientService.class);}配置关系
4.FactoryBean 创建员工类 public class Employee {public void check(){System.out.println(检查是否能够拿到员工类对象);}
}创建员工 factory 类实现 FactoryBean public class EmployeeFactory implements FactoryBeanEmployee {public Employee getObject() throws Exception {System.out.println(获取 emp 对象);return new Employee();}public Class? getObjectType() {return Employee.class;}public boolean isSingleton() {return false;}
}配置工厂类(并没有直接配置 emp 类) bean idemployee classcn.sycoder.domian.EmployeeFactory/bean获取 emp 对象 Testpublic void testFactoryBeanInit(){final ClassPathXmlApplicationContext context new ClassPathXmlApplicationContext(beans.xml);final Employee emp (Employee)context.getBean(employee);emp.check();}实现方法说明 isSingleton:如果是 true 返回单例的对象 public boolean isSingleton() {return true;}getObject:进行对象创建的 public Employee getObject() throws Exception {System.out.println(获取 emp 对象);return new Employee();
}
