跟随小破站学习java spring框架第五天

技术2022-07-15 82

主讲singleton(单例模式) 和 prototype(多例模式)的区别

<bean id="student" class="com.atguigu.ioc.scope.Student" scope="singleton"> <property name="sid" value="1001"></property> <property name="sname" value="张三"></property> </bean> public class Student { private Integer sid; private String sname; public Integer getSid() { return sid; } public void setSid(Integer sid) { this.sid = sid; } public String getSname() { return sname; } public void setSname(String sname) { this.sname = sname; } public Student() { System.out.println("Student的构造方法"); } } public class Test { public static void main(String[] args) { /** * 若spring中有单例模式的bean，在初始化容器时就会创建此对象 * 而多例即原型的bean,会在使用时创建 */ ApplicationContext ac = new ClassPathXmlApplicationContext("scope.xml"); Student student1 = ac.getBean("student", Student.class); Student student2 = ac.getBean("student", Student.class); System.out.println(student1); System.out.println(student2); } } //当.xml文件中给bean标签设置为单例模式时构造器只调用了一次 //当.xml文件中给bean标签设置为多例模式时构造器调用多次 //若设置为单例模式时,系统会默认加载构造器

public class Person { private Integer id; private String sex; private String name; public Integer getId() { return id; } public void setId(Integer id) { System.out.println("Two:依赖注入"); this.id = id; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Person() { System.out.println("One:创建对象"); } @Override public String toString() { return "Four:使用"; } public void init(){ System.out.println("Three:初始化"); } public void destory(){ System.out.println("Five:销毁"); } } <bean id="person" class="com.atguigu.ioc.life.Person" init-method="init" destroy-method="destory"> <property name="id" value="1001"></property> <property name="sex" value="男"></property> </bean> public class Test { public static void main(String[] args) { ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("life.xml"); Person person = ac.getBean("person",Person.class); System.out.println(person); ac.close(); } } //在.xml bean标签中通过设置init-method(初始化方法)和destroy-method(销毁方法)来调用类中自己编写的方法 //销毁方法只有在资源对象关闭之后才会调用

将原本的5步生命周期增加到7步可以通过后置处理器对方法进行再次编写

<bean class="com.atguigu.ioc.life.AfterHandler"></bean> //bean的后置处理器新增的2步 public class AfterHandler implements BeanPostProcessor { //初始化之前 @Override public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { Person person = (Person)bean; if(person.getSex().equals("男")){ person.setName("张无忌"); }else{ person.setName("赵敏"); } return person; } //初始化之后 @Override public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { // TODO Auto-generated method stub return bean; } } //注：若实现接口重写方法时括号内为object o 说明需要导入源码!

//方式一:直接引用 <bean id="datasource1" class="com.alibaba.druid.pool.DruidDataSource"> <property name="driverClassName" value="com.mysql.jdbc.Driver"></property> <property name="url" value="jdbc:mysql://localhost:3306/test"></property> <property name="username" value="root"></property> <property name="password" value="123456"></property> </bean> public class Test { public static void main(String[] args) throws Exception { ApplicationContext ac = new ClassPathXmlApplicationContext("datasource.xml"); DruidDataSource bean = ac.getBean("datasource1", DruidDataSource.class); System.out.println(bean.getConnection()); } } //方式二:使用jdbc方式此方法需要事先加载资源文件 db.properties # k = v jdbc.driver=com.mysql.jdbc.Driver jdbc.url=jdbc:mysql://localhost:3306/test jdbc.username=root jdbc.password=123456  <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="location" value="db.properties"></property> </bean> <bean id="datasource" class="com.alibaba.druid.pool.DruidDataSource"> <property name="driverClassName" value="${jdbc.driver}"></property> <property name="url" value="${jdbc.url}"></property> <property name="username" value="${jdbc.username}"></property> <property name="password" value="${jdbc.password}"></property> </bean> 方式三:直接调用properties <context:property-placeholder location="db.properties"/>

public class Emp { private Integer eid; private String ename; //兼容性问题子类可以为父类所赋值 private CarExtends car; //兼容性问题实现类可以为接口赋值 private DeptI dept; public Integer getEid() { return eid; } public void setCar(CarExtends car) { this.car = car; } public void setDept(DeptI dept) { this.dept = dept; } public void setEid(Integer eid) { this.eid = eid; } public String getEname() { return ename; } public void setEname(String ename) { this.ename = ename; } public CarExtends getCar() { return car; } public DeptI getDept() { return dept; } @Override public String toString() { return "Emp [eid=" + eid + ", ename=" + ename + ", car=" + car + ", dept=" + dept + "]"; } } public class Car extends CarExtends { private Integer cid; private String cname; public Integer getCid() { return cid; } public void setCid(Integer cid) { this.cid = cid; } public String getCname() { return cname; } public void setCname(String cname) { this.cname = cname; } @Override public String toString() { return "Car [cid=" + cid + ", cname=" + cname + "]"; } } public class Dept implements DeptI{ private Integer did; private String dname; public Integer getDid() { return did; } public void setDid(Integer did) { this.did = did; } public String getDname() { return dname; } public void setDname(String dname) { this.dname = dname; } @Override public String toString() { return "Dept [did=" + did + ", dname=" + dname + "]"; } } //autowire 自动装配免去使用ref 可以byName/byType //byName时 id与class类型必须同名否则无法转换! //byType可不同名  <bean id="emp" class="com.atguigu.ioc.auto.Emp" autowire="byType"> <property name="eid" value="1001"></property> <property name="ename" value="张三"></property> </bean> <bean id="car1" class="com.atguigu.ioc.auto.Car"> <property name="cid" value="666666"></property> <property name="cname" value="霸道"></property> </bean> <bean id="dept1" class="com.atguigu.ioc.auto.Dept"> <property name="did" value="11111"></property> <property name="dname" value="研发部"></property> </bean> public class Test { public static void main(String[] args) { ApplicationContext ac = new ClassPathXmlApplicationContext("auto.xml"); Emp emp = ac.getBean("emp", Emp.class); System.out.println(emp); } }

所有注解都是功能相同的由@Component演变

@Controller //表示此处为控制层 public class UserController { public UserController(){ System.out.println("UserController"); } } @Service //接口无法写入bean中 public class UserServiceImpl implements UserService{ public UserServiceImpl(){ System.out.println("UserServiceImpl"); } } @Repository public class UserDaoImpl implements UserDao { public UserDaoImpl(){ System.out.println("UserDaoImpl"); } }  <context:component-scan base-package="com.atguigu.ioc.userMod"></context:component-scan>  public class Test { public static void main(String[] args) { ApplicationContext ac = new ClassPathXmlApplicationContext("user.xml"); UserController uc = ac.getBean("userController",UserController.class); System.out.println(uc); UserService us = ac.getBean("userServiceImpl",UserServiceImpl.class); System.out.println(us); UserDao ud = ac.getBean("userDaoImpl",UserDaoImpl.class); System.out.println(ud); //1.在类上加注解将需要被spring管理的对象所属的类上加注解 //2.扫描组件在spring配置文件下加上一个组件扫描<context:component-scan> 使用包结构 //只有创建容器语句时也可正确运行需导入aop.jar! } }

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