DI
1.概述
- 概述:Dependency Injection 依赖注入,给对象设置属性,曾经我们需要自己去创建 mapper 对象,才能调用,现在交给 spring 创建,并且使用 DI 注入,直接拿来用,程序员就可以更加关注业务代码而不是创建对象(ioc已经创建好了对象,通过DI来拿到对象使用)
- 给对象设置属性方式:
- 构造器
- set 方法
- spring 也是通过构造器以及set方法来实现属性设置
2.回顾问题
-
如果只给了 mapper 对象,那么调用的时候会出现空指针
-
解决方式:使用 DI 注入,解决方案如下
3.构造器依赖注入
3.1.创建学生类
public class Student {
}
3.2.创建Mapper 接口以及实现类
-
创建 Mapper 接口
public interface StudentMapper {void insert(Student stu);int delete(Long id); }
-
创建 Mapper 实现类
public class StudentMapperImpl implements StudentMapper{public void insert(Student stu) {System.out.println("保存学生信息");}public int delete(Long id) {System.out.println("删除id="+id+"的学生信息");return 1;} }
-
将 Mapper 交给容器管理
<bean id="studentMapper" class="cn.sycoder.di.mapper.StudentMapperImpl"></bean>
3.3.创建 service 接口以及实现类
-
创建 service 接口
public interface IStudentService {void insert(Student stu);int delete(Long id); }
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创建 service 实现类
public class StudentServiceImpl implements IStudentService {private StudentMapper mapper;public void insert(Student stu) {mapper.insert(stu);}public int delete(Long id) {return mapper.delete(id);} }
-
将 service 交给容器管理
<bean id="iStudentService" class="cn.sycoder.di.service.impl.StudentServiceImpl"></bean>
3.4.如果没有使用DI注入直接调用
-
会产生如下问题
3.5.配置构造器注入属性
-
配置 service 构造器
public class StudentServiceImpl implements IStudentService {private StudentMapper mapper;public StudentServiceImpl(StudentMapper mapper){this.mapper = mapper;}public void insert(Student stu) {mapper.insert(stu);}public int delete(Long id) {return mapper.delete(id);} }
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配置 xml
<!-- 配置 service--><bean id="iStudentService" class="cn.sycoder.di.service.impl.StudentServiceImpl"><constructor-arg name="mapper" ref="studentMapper"></constructor-arg></bean> <!-- 配置 mapper--><bean id="studentMapper" class="cn.sycoder.di.mapper.StudentMapperImpl"></bean>
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注意:
-
name:构造器的参数名称
-
ref:配置文件中其它 bean 的名称
-
图示如下
-
3.6.构造器配置多个引用类型参数
-
service
public class StudentServiceImpl implements IStudentService {private StudentMapper mapper;private UserMapper userMapper;public StudentServiceImpl(StudentMapper mapper,UserMapper userMapper){this.mapper = mapper;this.userMapper = userMapper;}public void insert(Student stu) {mapper.insert(stu);}public int delete(Long id) {userMapper.delete(id);return mapper.delete(id);} }
-
mapper
public interface UserMapper {int delete(Long id); }
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mapper 实现类
public class UserMapperImpl implements UserMapper{public int delete(Long id) {System.out.println("删除id="+id+"的用户信息");return 1;} }
-
配置
<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"> <!-- 配置 service--><bean id="iStudentService" class="cn.sycoder.di.service.impl.StudentServiceImpl"><constructor-arg name="mapper" ref="studentMapper"></constructor-arg><constructor-arg name="userMapper" ref="userMapper"></constructor-arg></bean> <!-- 配置学生mapper--><bean id="studentMapper" class="cn.sycoder.di.mapper.StudentMapperImpl"></bean> <!-- 配置用户mapper--><bean id="userMapper" class="cn.sycoder.di.mapper.UserMapperImpl"></bean> </beans>
3.7.构造器配置多个基本数据类型参数
-
service
public class StudentServiceImpl implements IStudentService {private String name;private int age;private StudentMapper mapper;private UserMapper userMapper;public StudentServiceImpl(String name,int age,StudentMapper mapper,UserMapper userMapper){this.name = name;this.age = age;this.mapper = mapper;this.userMapper = userMapper;}public void insert(Student stu) {mapper.insert(stu);}public int delete(Long id) {System.out.println( name+":"+age);userMapper.delete(id);return mapper.delete(id);} }
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xml
<?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"> <!-- 配置 service--><bean id="iStudentService" class="cn.sycoder.di.service.impl.StudentServiceImpl"><constructor-arg name="userMapper" ref="userMapper"></constructor-arg><constructor-arg name="mapper" ref="studentMapper"></constructor-arg><constructor-arg type="int" value="18"></constructor-arg><constructor-arg type="java.lang.String" value="sy"></constructor-arg></bean> <!-- 配置学生mapper--><bean id="studentMapper" class="cn.sycoder.di.mapper.StudentMapperImpl"></bean> <!-- 配置用户mapper--><bean id="userMapper" class="cn.sycoder.di.mapper.UserMapperImpl"></bean> </beans>
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这种方式会存在参数覆盖的问题,解决方式,删除 type 添加 index 属性
<?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"> <!-- 配置 service--><bean id="iStudentService" class="cn.sycoder.di.service.impl.StudentServiceImpl"><constructor-arg name="userMapper" ref="userMapper"></constructor-arg><constructor-arg name="mapper" ref="studentMapper"></constructor-arg><constructor-arg index="2" value="18"></constructor-arg><constructor-arg index="1" value="1"></constructor-arg><constructor-arg type="java.lang.String" value="sy"></constructor-arg></bean> <!-- 配置学生mapper--><bean id="studentMapper" class="cn.sycoder.di.mapper.StudentMapperImpl"></bean> <!-- 配置用户mapper--><bean id="userMapper" class="cn.sycoder.di.mapper.UserMapperImpl"></bean> </beans>
4.setter依赖注入
-
使用 set 方法实现属性的注入
-
使用 property 属性
- name:属性名称
- value:直接给值
- ref:其它bean的引用
4.1.创建员工类
public class Employee {
}
4.2.创建 mapper 接口以及实现类
-
mapper 接口
public interface EmployeeMapper {int delete(Long id); }
-
mapper 实现类
public class EmployeeMapperImpl implements EmployeeMapper {public int delete(Long id) {System.out.println("删除当前员工id:"+id);return 1;} }
4.3.创建 servie 接口以及实现类
-
创建 service 接口
public interface IEmployeeService {int delete(Long id); }
-
创建 service 接口实现类
public class EmployeeServiceImpl implements IEmployeeService {private EmployeeMapper mapper;public int delete(Long id) {return mapper.delete(id);} }
4.4.配置 setter 注入
-
配置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"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><!-- 配置mapper实现类--> <!-- 配置mapper--><bean id="empMapper" class="cn.sycoder.di.setter.mapper.EmployeeMapperImpl"></bean> <!-- 配置service--><bean id="empService" class="cn.sycoder.di.setter.service.impl.EmployeeServiceImpl"></bean> </beans>
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service 实现中提供 mapper 的setter 方法
public class EmployeeServiceImpl implements IEmployeeService {private EmployeeMapper employeeMapper;public int delete(Long id) {return employeeMapper.delete(id);}public void setEmployeeMapper(EmployeeMapper employeeMapper){this.employeeMapper = employeeMapper;} }
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修改 beans.xml 通过 setter 注入
<?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"><!-- 配置mapper实现类--> <!-- 配置mapper--><bean id="empMapper" class="cn.sycoder.di.setter.mapper.EmployeeMapperImpl"></bean> <!-- 配置service--><bean id="empService" class="cn.sycoder.di.setter.service.impl.EmployeeServiceImpl"><property name="employeeMapper" ref="empMapper"></property></bean> </beans>
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获取 service 执行 delete 方法
@Testpublic void testSetDi(){final ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("DiSetterBeans.xml");final IEmployeeService empService = (IEmployeeService) context.getBean("empService");empService.delete(2L);}
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setter 注入过程分析
4.5.配置多个 setter 方法注入多个属性
-
给service 添加新的属性以及新的setter方法
public class EmployeeServiceImpl implements IEmployeeService {private EmployeeMapper employeeMapper;private UserMapper userMapper;public int delete(Long id) {return employeeMapper.delete(id);}public void setEmployeeMapper(EmployeeMapper employeeMapper){System.out.println("=======使用 setter 注入=======");this.employeeMapper = employeeMapper;}public void setUserMapper(UserMapper mapper){this.userMapper = mapper;} }
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配置 userMapper 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"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><!-- 配置mapper实现类--> <!-- 配置mapper--><bean id="empMapper" class="cn.sycoder.di.setter.mapper.EmployeeMapperImpl"></bean> <!-- 配置service--><bean id="empService" class="cn.sycoder.di.setter.service.impl.EmployeeServiceImpl"><property name="employeeMapper" ref="empMapper"></property></bean> <!-- 配置 userMapper--><bean id="userMapper" class="cn.sycoder.di.constructor.mapper.StudentMapperImpl"></bean> </beans>
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通过 setter 注入
<?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"><!-- 配置mapper实现类--> <!-- 配置mapper--><bean id="empMapper" class="cn.sycoder.di.setter.mapper.EmployeeMapperImpl"></bean> <!-- 配置service--><bean id="empService" class="cn.sycoder.di.setter.service.impl.EmployeeServiceImpl"><property name="employeeMapper" ref="empMapper"></property><property name="userMapper" ref="userMapper"></property></bean> <!-- 配置 userMapper--><bean id="userMapper" class="cn.sycoder.di.constructor.mapper.UserMapperImpl"></bean> </beans>
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获取 service 操作delete 方法
@Testpublic void testSetterSDi(){final ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("DiSetterBeans.xml");final IEmployeeService empService = (IEmployeeService) context.getBean("empService");empService.delete(2L);}
4.6.使用 setter 注入简单类型
-
修改 service 类,提供两个属性 int age = 18,String name = “sy”
public class EmployeeServiceImpl implements IEmployeeService {private EmployeeMapper employeeMapper;private UserMapper userMapper;private String name;private int age;public void setName(String name){this.name = name;}public void setAge(int age){this.age = age;}public int delete(Long id) {System.out.println(name + ":" + age);userMapper.delete(id);return employeeMapper.delete(id);}public void setEmployeeMapper(EmployeeMapper employeeMapper){System.out.println("=======EmployeeMapper使用 setter 注入=======");this.employeeMapper = employeeMapper;}public void setUserMapper(UserMapper mapper){System.out.println("=======UserMapper使用 setter 注入=======");this.userMapper = mapper;} }
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配置 xml 设置值
<?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"><!-- 配置mapper实现类--> <!-- 配置mapper--><bean id="empMapper" class="cn.sycoder.di.setter.mapper.EmployeeMapperImpl"></bean> <!-- 配置service--><bean id="empService" class="cn.sycoder.di.setter.service.impl.EmployeeServiceImpl"><property name="employeeMapper" ref="empMapper"></property><property name="userMapper" ref="userMapper"></property><property name="name" value="sy"></property><property name="age" value="18"></property></bean> <!-- 配置 userMapper--><bean id="userMapper" class="cn.sycoder.di.constructor.mapper.UserMapperImpl"></bean> </beans>
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可能出现的问题
4.7.setter 注入总结
- 对于引用数据类型来说使用
- < property name=“” ref=“”>
- 对于简单数据类型
- < property name=“” value=“”>
5.集合注入
- List
- Set
- Map
- Array
- Properties
5.1.添加CollectiosDemo类
public class CollectionsDemo {private List<Integer> list;private Map<String,String> map;private Set<String> set;private Properties properties;private int[] arr;public void print(){System.out.println("list:"+list);System.out.println("map:"+map);System.out.println("set:"+set);System.out.println("properties:"+properties);System.out.println("arr:"+ Arrays.toString(arr));}public void setList(List<Integer> list) {this.list = list;}public void setMap(Map<String, String> map) {this.map = map;}public void setSet(Set<String> set) {this.set = set;}public void setProperties(Properties properties) {this.properties = properties;}public void setArr(int[] arr) {this.arr = arr;}
}
5.2.配置 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"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><bean id="collectionsDemo" class="cn.sycoder.collections.CollectionsDemo">
<!-- 注入 list--><property name="list"><list><value>1</value><value>2</value><value>3</value></list></property><property name="map"><map><entry key="name" value="sy"/><entry key ="age" value="18"/></map></property><property name="set"><set><value>just some string</value><value>just string</value></set></property><property name="properties"><props><prop key="url">@example.org</prop><prop key="user">root</prop><prop key="password">123456</prop></props></property><property name="arr"><array><value>2</value><value>2</value><value>2</value></array></property></bean>
</beans>
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如果不提供setter 方法会出现如下错误
6.自动装配
1.概述
- 概述:IOC容器根据bean所依赖的属性,自动查找并进行自动装配。
2.分类
- 不启用自动装配
- byName 通过名称
- byType 通过类型
- constructor 通过构造器
3.实操
-
准备工作
public class EmployeeService {private EmployeeMapperImpl employeeMapper;public int delete(Long id) {return employeeMapper.delete(id);}public void setEmployeeMapper(EmployeeMapperImpl employeeMapper){System.out.println("=======EmployeeMapper使用 setter 注入=======");this.employeeMapper = employeeMapper;} }
public class EmployeeMapperImpl{public int delete(Long id) {System.out.println("删除当前员工id:"+id);return 1;} }
-
配置 bean 并且通过 bype 自动装配
<?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 id="empService" class="cn.sycoder.autowired.EmpService" autowire="byType"></bean><bean id="empMapperImpl" class="cn.sycoder.autowired.EmpMapperImpl"></bean></beans>
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配置 bean 并且通过 byName 自动装配
<?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 id="empService" class="cn.sycoder.autowired.EmpService" autowire="byName"></bean><bean id="empMapperImpl" class="cn.sycoder.autowired.EmpMapperImpl"></bean></beans>
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通过名称和类型的自动装配
-
byName
- 使用 id 或者是 name 别名
- 如果自动注入时,有多个相同对象,只能使用 byName
-
byType
-
根据类型注入
-
通过 byType 注入要保证容器中只有一个 bean 对象,否则会出现如下错误
-
-
-
注意:
- 自动注入的优先级是低于 setter 和 构造器注入的
- 自动注入只能用于引用类型,不能用于基本数据类型
- 推荐使用 byType 方式实现自动注入
- 注入流程
- byType 根据 getClass 去注入
- byName 根据属性名称去注入
7.bean scopes
-
常见的作用域
作用域 说明 singleton 单例的 prototype 多例 request 请求 session 会话 -
单例 singleton
-
修改对象变成多个实例的
-
注意:容器模式就是以单例的方式创建对象的,如果需要修改成非单例,使用 scope 属性修改即可
-
以后开发中适合将那些bean对象交给 spring 管理
- 持久层 mapper
- 业务层 service
- 控制层 controller
-
单例bean会出现线程安全吗
- 判断bean 对象是否存储数据,如果用来存储数据了,会导致线程安全问题
- 使用局部变量做存储,方法调用结束就销毁了,所以不存在线程安全问题
8.bean 生命周期
1.概述
- 概述:生命周期就是一个对象从出生到死亡的过程
2.使用用户类观察生命周期
-
创建用户类
public class User {private String name;public User(){System.out.println("构造器执行====");}public void setName(String name) {System.out.println("调用 set 方法");this.name = name;}public void init(){System.out.println("调用 init 方法");}public void destroy(){System.out.println("调用销毁方法");} }
-
配置 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"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><bean id="user" class="cn.sycoder.lifecycle.User" init-method="init" destroy-method="destroy"><property name="name" value="sy"></property></bean> </beans>
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获取 bean 出现如下问题,没有打印销毁方法
-
原因:
-
spring ioc 容器是运行在 jvm 虚拟机中的
-
执行 test 方法后 jvm 虚拟机开启,spring 加载配置文件创建 bean 对象,调用构造器以及 init 方法
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test 方法执行完毕的时候, jvm 退出,spring ioc 容器来不及关闭销毁 bean,所以没有去调用 destroy 方法
-
-
解决办法,正常关闭容器
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3.BeanPostProcessor
-
自定义自己 bean 处理器
public class MyBeanPostProcessor implements BeanPostProcessor{public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {//bean 前置处理器System.out.println("bean 的前置处理器");return bean;}public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {System.out.println("bean 的后置处理器");//bean 后置处理器return bean;} }
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配置 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"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><bean id="user" class="cn.sycoder.lifecycle.User" init-method="init" destroy-method="destroy"><property name="name" value="sy"></property></bean><bean class="cn.sycoder.lifecycle.MyBeanPostProcessor"></bean> </beans>
4.生命周期总结
- bean 对象创建(调用无参构造器)
- 设置属性通过 setter 方法
- init 方法前调用 bean 的前置处理器
- bean 的 init 方法
- bean 的后置处理器
- 对象可以正常使用
- destroy 销毁方法
- ioc 容器关闭
- jvm 虚拟机的退出