Java Spring Bean工厂后处理器 Java Spring Bean工厂后处理器Spring的后处理器是Spring对外开发的重要扩展点，允许我们介入到Bean的整个实例化流程中来，以达到动态注册BeanDefinition，动态修改BeanDefinition，以及动态修改Bean的作用。Spring主要有两种后处理器:BeanFactoryPostProcessor: Bean工厂后处理器，在BeanDefinitionMap填充完毕，Bean实例化之前执行；BeanPostProcessor: Bean后处理器，一般在Bean实例化之后，填充到单例池singletonObjects之前执行。1. BeanFactoryPostProcessor1.1 快速入门BeanFactoryPostProcessor是一个接口规范，实现了该接口的类只要交由Spring容器管理的话，那么Spring就会回调该接口的方法，用于对BeanDefinition注册和修改的功能。实例化流程MyBeanFactoryPostProcessor.javapackage processor; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.BeanFactoryPostProcessor; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor { @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException { System.out.println("beanDefinitionMap填充完毕后回调该方法"); } } beans.xml<bean class="processor.MyBeanFactoryPostProcessor"/>主函数断点调试public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); }执行结果beanDefinitionMap填充完毕后回调该方法1.2 强制修改BeanDefinition其他设置基于上文MyBeanFactoryPostProcessor.javapublic class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor { @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException { System.out.println("beanDefinitionMap填充完毕后回调该方法"); BeanDefinition beanDefinition = configurableListableBeanFactory.getBeanDefinition("userService"); beanDefinition.setBeanClassName("org.example.UserDaoImpl"); } }主函数调用public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); Object userService = applicationContext.getBean("userService"); System.out.println(userService); }输出结果beanDefinitionMap填充完毕后回调该方法 org.example.UserDaoImpl@3c875211.3 动态注入BeanDefinition创建一个新的接口PersonDaopublic interface PersonDao { }创建一个新的类PersonDaoImpl，并且继承PersonDao接口public class PersonDaoImpl implements PersonDao{ }MyBeanFactoryPostProcessor.javapublic class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor { @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException { System.out.println("beanDefinitionMap填充完毕后回调该方法"); //注册BeanDefinition BeanDefinition beanDefinition = new RootBeanDefinition(); beanDefinition.setBeanClassName(PersonDaoImpl.class.getName()); //强转为DefaultListableBeanFactory DefaultListableBeanFactory defaultListableBeanFactory = (DefaultListableBeanFactory) configurableListableBeanFactory; defaultListableBeanFactory.registerBeanDefinition("personDao",beanDefinition); } }beans.xml<bean class="processor.MyBeanFactoryPostProcessor"/>主函数调用 public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); PersonDao personDao = applicationContext.getBean(PersonDao.class); System.out.println(personDao); }执行结果beanDefinitionMap填充完毕后回调该方法 org.example.PersonDaoImpl@780cb77_Spring 提供了一个BeanFactoryPostProcessor的子接口BeanDefinitionRegistryPostProcessor专门用于注册BeanDefinition操作直接继承BeanDefinitionRegistryPostProcessor接口的方式简化代码MyBeanDefinitionRegistryPostProcessor.javapackage processor; import org.example.PersonDaoImpl; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.BeanDefinition; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; import org.springframework.beans.factory.support.BeanDefinitionRegistry; import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor; import org.springframework.beans.factory.support.RootBeanDefinition; public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor { @Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException { System.out.println("beanDefinitionMap填充完毕后回调该方法"); //注册BeanDefinition BeanDefinition beanDefinition = new RootBeanDefinition(); beanDefinition.setBeanClassName(PersonDaoImpl.class.getName()); beanDefinitionRegistry.registerBeanDefinition("personDao",beanDefinition); } @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException { } } beans.xml<bean class="processor.MyBeanDefinitionRegistryPostProcessor"/>主函数调用 public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); PersonDao personDao = applicationContext.getBean(PersonDao.class); System.out.println(personDao); }执行结果beanDefinitionMap填充完毕后回调该方法 org.example.PersonDaoImpl@50a7bc6e1.4使用Spring的BeanFactoryPostProcessor扩展点完成自定义注解扫描要求如下：自定义@MyComponent注解，使用在类上;使用资料中提供好的包扫描器工具BaseClassScanUtils 完成指定包的类扫描自定义BeanFactoryPostProcessor完成注解@MyComponent的解析，解析后最终被Spring管理。黑马程序员提供的BaseClassScanUtils.javapackage com.itheima.utils; import org.springframework.core.io.Resource; import org.springframework.core.io.support.PathMatchingResourcePatternResolver; import org.springframework.core.io.support.ResourcePatternResolver; import org.springframework.core.type.classreading.CachingMetadataReaderFactory; import org.springframework.core.type.classreading.MetadataReader; import org.springframework.core.type.classreading.MetadataReaderFactory; import org.springframework.util.ClassUtils; import java.lang.annotation.Annotation; import java.util.HashMap; import java.util.List; import java.util.Map; public class BaseClassScanUtils { //设置资源规则 private static final String RESOURCE_PATTERN = "/**/*.class"; public static Map<String, Class> scanMyComponentAnnotation(String basePackage) { //创建容器存储使用了指定注解的Bean字节码对象 Map<String, Class> annotationClassMap = new HashMap<String, Class>(); //spring工具类，可以获取指定路径下的全部类 ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver(); try { String pattern = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX + ClassUtils.convertClassNameToResourcePath(basePackage) + RESOURCE_PATTERN; Resource[] resources = resourcePatternResolver.getResources(pattern); //MetadataReader 的工厂类 MetadataReaderFactory refractory = new CachingMetadataReaderFactory(resourcePatternResolver); for (Resource resource : resources) { //用于读取类信息 MetadataReader reader = refractory.getMetadataReader(resource); //扫描到的class String classname = reader.getClassMetadata().getClassName(); Class<?> clazz = Class.forName(classname); //判断是否属于指定的注解类型 if(clazz.isAnnotationPresent(MyComponent.class)){ //获得注解对象 MyComponent annotation = clazz.getAnnotation(MyComponent.class); //获得属value属性值 String beanName = annotation.value(); //判断是否为"" if(beanName!=null&&!beanName.equals("")){ //存储到Map中去 annotationClassMap.put(beanName,clazz); continue; } //如果没有为"",那就把当前类的类名作为beanName annotationClassMap.put(clazz.getSimpleName(),clazz); } } } catch (Exception exception) { } return annotationClassMap; } public static void main(String[] args) { Map<String, Class> stringClassMap = scanMyComponentAnnotation("com.itheima"); System.out.println(stringClassMap); } }由于我使用的是jdk19，所以使用上述文件会提示版本错误，所以在上面的基础上进行修改package utils; import anno.MyComponent; import org.springframework.core.io.Resource; import org.springframework.core.io.support.PathMatchingResourcePatternResolver; import org.springframework.core.io.support.ResourcePatternResolver; import org.springframework.util.ClassUtils; import java.util.HashMap; import java.util.Map; public class BaseClassScanUtils { //设置资源规则 private static final String RESOURCE_PATTERN = "/**/*.class"; public static Map<String, Class> scanMyComponentAnnotation(String basePackage) { //创建容器存储使用了指定注解的Bean字节码对象 Map<String, Class> annotationClassMap = new HashMap<String, Class>(); //spring工具类，可以获取指定路径下的全部类 ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver(); try { String pattern = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX + ClassUtils.convertClassNameToResourcePath(basePackage) + RESOURCE_PATTERN; Resource[] resources = resourcePatternResolver.getResources(pattern); for (Resource resource : resources) { Class<?> clazz = Class.forName(resource.getFile().toString().split("classes\\\\")[1].replaceAll("\\\\",".").split(".class")[0]); //判断是否属于指定的注解类型 if(clazz.isAnnotationPresent(MyComponent.class)){ //获得注解对象 MyComponent annotation = clazz.getAnnotation(MyComponent.class); //获得属value属性值 String beanName = annotation.value(); //判断是否为"" if(beanName!=null&&!beanName.equals("")){ //存储到Map中去 annotationClassMap.put(beanName,clazz); continue; } //如果没有为"",那就把当前类的类名作为beanName annotationClassMap.put(clazz.getSimpleName(),clazz); } } } catch (Exception exception) { System.out.println(exception); } return annotationClassMap; } public static void main(String[] args) { Map<String, Class> stringClassMap = scanMyComponentAnnotation("beans"); System.out.println(stringClassMap); } }创建注解MyComponentpackage anno; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) public @interface MyComponent { String value(); }创建类并且添加MyComponent注解，类位于beans目录下package beans; import anno.MyComponent; @MyComponent("otherBean") public class OtherBean { }创建新的后工厂处理器类，并且继承BeanDefinitionRegistryPostProcessor接口package processor; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.BeanDefinition; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; import org.springframework.beans.factory.support.BeanDefinitionRegistry; import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor; import org.springframework.beans.factory.support.RootBeanDefinition; import utils.BaseClassScanUtils; import java.util.Map; public class MyComponentBeanFactoryPostProcessor implements BeanDefinitionRegistryPostProcessor { @Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException { // 使用扫描工具去扫描指定包以及子包下的所有类，收集使用@Mycomponent的注解的类 Map<String, Class> myComponentAnnotation = BaseClassScanUtils.scanMyComponentAnnotation("beans"); // 遍历Map，组装BeanDefinition进行注册 myComponentAnnotation.forEach((beanName,clazz)->{ // 获取类名 String beanClassName = clazz.getName(); // 创建BeanDefinition BeanDefinition beanDefinition = new RootBeanDefinition(); beanDefinition.setBeanClassName(beanClassName); // 注册BeanDefinition beanDefinitionRegistry.registerBeanDefinition(beanName ,beanDefinition); }); } @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException { } } 在beans.xml中添加后工厂处理器<bean class="processor.MyComponentBeanFactoryPostProcessor"/>主函数调用public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); OtherBean otherBean = applicationContext.getBean(OtherBean.class); System.out.println(otherBean); }执行结果beans.OtherBean@2133814f2. BeanPostProcessor2.1 快速入门Bean被实例化后，到最终缓存到名为singletonObjects单例池之前，中间会经过Bean的初始化过程，例如: 属性的填充、初始方法init的执行等，其中有一个对外进行扩展的点BeanPostProcessor，我们称为Bean后处理。跟上面的Bean工厂后处理器相似，它也是一个接口，实现了该接口并被容器管理的BeanPostProcessor，会在流程节点上被Spring自动调用。BeanPostProcessor类public interface BeanPostProcessor { @Nullable default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { return bean; } @Nullable default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { return bean; } }UserDaopackage org.example; public interface UserDao { }UserDaoImplpackage org.example; public class UserDaoImpl implements UserDao { String name; public UserDaoImpl() { System.out.println("UserDaoImpl初始化"); } public String getName() { return name; } public void setName(String name) { System.out.println("设置name的值为" + name); this.name = name; } }创建MyBeanPostProcessor并且继承BeanPostProcessor接口public class MyBeanPostProcessor implements BeanPostProcessor { @Override public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { System.out.println("before-" + beanName + ":" + bean.toString()); if (bean instanceof UserDaoImpl){ UserDaoImpl userDao = (UserDaoImpl) bean; userDao.setName("hhhhh"); } return BeanPostProcessor.super.postProcessBeforeInitialization(bean, beanName); } @Override public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { System.out.println("after-" + beanName + ":" + bean.toString()); return BeanPostProcessor.super.postProcessAfterInitialization(bean, beanName); } }beans.xml<bean class="processor.MyBeanPostProcessor"/> <bean class="org.example.UserDaoImpl" id="userDao"/>主函数执行public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); UserDaoImpl userDao = (UserDaoImpl) applicationContext.getBean("userDao"); System.out.println(userDao.getName()); }执行结果UserDaoImpl初始化 before-userDao:org.example.UserDaoImpl@646be2c3 设置name的值为hhhhh after-userDao:org.example.UserDaoImpl@646be2c3 hhhhh2.2 before和after方法的执行时机基于上述快速入门的文件进行修改UserDaoImpl.javapackage org.example; import org.springframework.beans.factory.InitializingBean; public class UserDaoImpl implements UserDao, InitializingBean { public UserDaoImpl() { System.out.println("UserDaoImpl初始化"); } String name; public String getName() { return name; } public void setName(String name) { System.out.println("设置name的值为" + name); this.name = name; } public void init(){ System.out.println("init初始化方法执行"); } @Override public void afterPropertiesSet() throws Exception { System.out.println("属性设置之后执行"); } }beans.xml<bean class="org.example.UserDaoImpl" id="userDao" init-method="init"/> <bean class="processor.MyBeanPostProcessor" />执行结果UserDaoImpl初始化 before-userDao:org.example.UserDaoImpl@3c0a50da 设置name的值为hhhhh 属性设置之后执行 init初始化方法执行 after-userDao:org.example.UserDaoImpl@3c0a50da hhhhh2.3 对Bean方法进行执行时间日志增强需求：Bean的方法执行之前控制台打印当前时间Bean的方法执行之后控制台打印当前时间分析：对方法进行增强主要就是代理设计模式和包装设计模式由于Bean方法不确定，所以使用动态代理在运行期间执行增强操作在Bean实例创建完毕后，进入到单例池之前，使用Proxy代替真是的目标BeanUserDao.javapackage org.example; public interface UserDao { public void show(); }UserDaoImpl.javapackage org.example; public class UserDaoImpl implements UserDao { public void show(){ System.out.println("执行方法中"); } }TimeLogBeanPostProcessor.javapackage processor; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.BeanPostProcessor; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.util.Date; public class TimeLogBeanPostProcessor implements BeanPostProcessor { @Override public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { Object beanProxy = Proxy.newProxyInstance(bean.getClass().getClassLoader(), bean.getClass().getInterfaces(), (Object proxy, Method method, Object[] args) -> { //1.输出开始时间 System.out.println("方法：" + method.getName() + "-开始时间：" + new Date()); //2.执行目标方法 Object result = method.invoke(bean,args); //3.输出结束时间 System.out.println("方法：" + method.getName() + "-结束时间：" + new Date()); return result; }); return beanProxy; } }beans.xml<bean class="processor.TimeLogBeanPostProcessor"/> <bean class="org.example.UserDaoImpl" id="userDao"/>主函数调用 public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); UserDao userDao = (UserDao) applicationContext.getBean("userDao"); userDao.show(); }执行结果方法：show-开始时间：Thu Mar 02 16:13:42 CST 2023 执行方法中 方法：show-结束时间：Thu Mar 02 16:13:43 CST 2023

Java Spring Bean实例化的基本流程 Java Spring Bean实例化的基本流程Spring容器在进行初始化时，会将xml配置的<bean>的信息封装成一个BeanDefinition对象，所有的BeanDefinition存储到一个名为beanDefinitionMap的Map集合中去，Spring框架在对该Map进行遍历，使用反射创建Bean实例对象，创建好的Bean对象存储在一个名为singletonObjects的Map集合中，当调用getBean方法时则最终从该Map集合中取出Bean实例对象返回。流程：加载xml配置文件，解析获取配置中的每个<bean>的信息，封装成一个个的BeanDefinition对象将BeanDefinition存储在一个名为beanDefinitionMap的Map<String,BeanDefinition>中;ApplicationContext底层遍历beanDefinitionMap，创建Bean实例对象 创建好的Bean实例对象，被存储到一个名为singletonObjects的Map<String,Object>中;当执行applicationContext.getBean(beanName)时，从singletonObjects去匹配Bean实例返回beans.xml <bean class="org.example.UserDaoImpl" id="userDao"/> <bean class="org.example.UserServiceImpl" id="userService"/>主函数断点调试运行 public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); }Bean信息定义对象-BeanDefinitionBeanDefinition.class// // Source code recreated from a .class file by IntelliJ IDEA // (powered by FernFlower decompiler) // package org.springframework.beans.factory.config; import org.springframework.beans.BeanMetadataElement; import org.springframework.beans.MutablePropertyValues; import org.springframework.core.AttributeAccessor; import org.springframework.core.ResolvableType; import org.springframework.lang.Nullable; public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement { String SCOPE_SINGLETON = "singleton"; String SCOPE_PROTOTYPE = "prototype"; int ROLE_APPLICATION = 0; int ROLE_SUPPORT = 1; int ROLE_INFRASTRUCTURE = 2; void setParentName(@Nullable String var1); @Nullable String getParentName(); void setBeanClassName(@Nullable String var1); @Nullable String getBeanClassName(); void setScope(@Nullable String var1); @Nullable String getScope(); void setLazyInit(boolean var1); boolean isLazyInit(); void setDependsOn(@Nullable String... var1); @Nullable String[] getDependsOn(); void setAutowireCandidate(boolean var1); boolean isAutowireCandidate(); void setPrimary(boolean var1); boolean isPrimary(); void setFactoryBeanName(@Nullable String var1); @Nullable String getFactoryBeanName(); void setFactoryMethodName(@Nullable String var1); @Nullable String getFactoryMethodName(); ConstructorArgumentValues getConstructorArgumentValues(); default boolean hasConstructorArgumentValues() { return !this.getConstructorArgumentValues().isEmpty(); } MutablePropertyValues getPropertyValues(); default boolean hasPropertyValues() { return !this.getPropertyValues().isEmpty(); } void setInitMethodName(@Nullable String var1); @Nullable String getInitMethodName(); void setDestroyMethodName(@Nullable String var1); @Nullable String getDestroyMethodName(); void setRole(int var1); int getRole(); void setDescription(@Nullable String var1); @Nullable String getDescription(); ResolvableType getResolvableType(); boolean isSingleton(); boolean isPrototype(); boolean isAbstract(); @Nullable String getResourceDescription(); @Nullable BeanDefinition getOriginatingBeanDefinition(); }

Java Spring 配置非自定义Bean Java Spring 配置非自定义Bean0.介绍实际开发中会使用第三方jar包中的功能类，这些Bean要想让Spring进行管理，也需要对其进行配置两个问题：被配置的Bean实例化方式是什么被配置的Bean是否需要注入必要属性1.配置Druid数据源交由Spring管理maven配置文件导入相应jar包pom.xml <dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.1.23</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.49</version> </dependency>beans.xml <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource"> <property name="driverClassName" value="com.mysql.jdbc.Driver" /> <property name="url" value="jdbc:mysql://localhost:3306/java"/> <property name="username" value="root"/> <property name="password" value="root"/> </bean>主函数调用 public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); Object dataSource = applicationContext.getBean("dataSource"); System.out.println(dataSource); }运行结果{ CreateTime:"2023-02-26 17:23:51", ActiveCount:0, PoolingCount:0, CreateCount:0, DestroyCount:0, CloseCount:0, ConnectCount:0, Connections:[ ] }2.配置Connection交由Spring管理Connection的产生是通过DriverManager的静态方法getConnection获取的，所以我们要用静态工厂的方式配置beans.xml（getConnection报红不用管） <bean id="connection" class="java.sql.DriverManager" factory-method="getConnection" scope="prototype"> <constructor-arg name="url" value="jdbc:mysql://localhost:3306/java"/> <constructor-arg name="user" value="root"/> <constructor-arg name="password" value="root"/> </bean>主函数调用 public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); Object connection = applicationContext.getBean("connection"); System.out.println(connection);; }执行结果（报错不用管，看到有类字节码地址输出即可）com.mysql.jdbc.JDBC4Connection@42a15bdc3.配置日期对象交由Spring管理原生使用日期对象 SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); Date date = simpleDateFormat.parse("2023-08-27 12:00:00"); System.out.println(date);结果输出Sun Aug 27 12:00:00 CST 2023配置日期对象交由Spring管理beans.xml <bean id="simpleDateFormat" class="java.text.SimpleDateFormat"> <constructor-arg name="pattern" value="yyyy-MM-dd HH:mm:ss"/> </bean> <bean id="date" factory-bean="simpleDateFormat" factory-method="parse"> <constructor-arg name="source" value="2023-08-27 12:00:00"/> </bean>主函数执行 ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); Object date1 = applicationContext.getBean("date"); System.out.println(date1);结果输出Sun Aug 27 12:00:00 CST 20234.配置MyBatis的SqlSessionFactory交由Spring管理导入MyBatis的相关坐标 <!-- mybatis框架 --> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.5</version> </dependency> <!-- mysql驱动 --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.49</version> </dependency>4.1 原生实现 // 静态工厂方法方式 InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml"); // 无参构造实例化 SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder(); // 实例工厂方法 SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream); System.out.println(sqlSessionFactory);执行结果org.apache.ibatis.session.defaults.DefaultSqlSessionFactory@79efed2d4.2 Bean实现resources目录下创建mybatis-config.xml<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "https://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/java"/> <property name="username" value="root"/> <property name="password" value="root"/> </dataSource> </environment> </environments> </configuration>beans.xml <!-- 静态工厂方法 --> <bean id="resources" class="org.apache.ibatis.io.Resources" factory-method="getResourceAsStream"> <constructor-arg name="resource" value="mybatis-config.xml"/> </bean> <!-- 无参构造实例化 --> <bean id="sqlSessionFactoryBuilder" class="org.apache.ibatis.session.SqlSessionFactoryBuilder"/> <!-- 实例工厂方法 --> <bean id="sqlSessionFactory" factory-bean="sqlSessionFactoryBuilder" factory-method="build"> <constructor-arg name="inputStream" ref="resources"/> </bean>主函数调用 ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); Object sqlSessionFactory = applicationContext.getBean("sqlSessionFactory"); System.out.println(sqlSessionFactory);执行结果org.apache.ibatis.session.defaults.DefaultSqlSessionFactory@5026735c

Java Spring 获取Bean的三种方式 Java Spring 获取Bean的三种方式

Java Spring beans的profile属性切换环境 Java Spring beans的profile属性切换环境<beans>标签，除了经常用的作为根标签外，还可以嵌套在根标签内，使用profile属性切换开发环境可以使用以下两种方式指定被激活的环境（dev为环境名）：使用命令行动态参数，虚拟机参数位置加载 -Dspring.profiles.active=dev使用代码的方式设置环境变量System.setProperty("spring.profiles.active","dev")beans.xml <bean class="org.example.UserDaoImpl" id="userDao"/> <bean class="org.example.UserServiceImpl" id="userService"/> <beans profile="dev"> <bean id="userService1" class="org.example.UserServiceImpl"/> </beans> <beans profile="test"> <bean id="userDao1" class="org.example.UserDaoImpl"/> </beans>主函数调用 public static void main(String[] args) { // 指定环境 System.setProperty("spring.profiles.active","dev"); ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); System.out.println(((UserService) applicationContext.getBean("userService"))); System.out.println(((UserDao) applicationContext.getBean("userDao"))); System.out.println(((UserService) applicationContext.getBean("userService1"))); System.out.println(((UserDao) applicationContext.getBean("userDao1"))); }执行结果org.example.UserServiceImpl@589b3632 org.example.UserDaoImpl@45f45fa1 org.example.UserServiceImpl@4c6e276e Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'userDao1' available