Spring手写Spring框架解析XML文件并实例化Bean对象-----Spring框架

╰半橙微兮° 2024-03-23 21:58 77阅读 0赞

>     <?xml version="1.0" encoding="UTF-8"?>
>     <project xmlns="http://maven.apache.org/POM/4.0.0"
>              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>              xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
>         <modelVersion>4.0.0</modelVersion>
>     
>         <groupId>org.myspringframework</groupId>
>         <artifactId>myspring</artifactId>
>         <version>1.0.0</version>
>         <packaging>jar</packaging>
>         <dependencies>
>             <dependency>
>     
>                 <groupId>org.dom4j</groupId>
>                 <artifactId>dom4j</artifactId>
>                 <version>2.1.3</version>
>             </dependency>
>             <dependency>
>                 <groupId>org.apache.logging.log4j</groupId>
>                 <artifactId>log4j-core</artifactId>
>                 <version>2.19.0</version>
>             </dependency>
>             <dependency>
>                 <groupId>org.apache.logging.log4j</groupId>
>                 <artifactId>log4j-slf4j2-impl</artifactId>
>                 <version>2.19.0</version>
>             </dependency>
>             
>             <dependency>
>                 <groupId>junit</groupId>
>                 <artifactId>junit</artifactId>
>                 <version>4.13.2</version>
>                 <scope>test</scope>
>             </dependency>
>             <dependency>
>                 <groupId>jaxen</groupId>
>                 <artifactId>jaxen</artifactId>
>                 <version>1.2.0</version>
>             </dependency>
>         </dependencies>
>         <properties>
>             <maven.compiler.source>17</maven.compiler.source>
>             <maven.compiler.target>17</maven.compiler.target>
>             <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
>         </properties>
>     
>     </project>
> 
>     <?xml version="1.0" encoding="UTF-8"?>
>     <project xmlns="http://maven.apache.org/POM/4.0.0"
>              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>              xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
>         <modelVersion>4.0.0</modelVersion>
>     
>         <groupId>org.myspringframework</groupId>
>         <artifactId>myspring</artifactId>
>         <version>1.0.0</version>
>         <packaging>jar</packaging>
>         <dependencies>
>             <dependency>
>     
>                 <groupId>org.dom4j</groupId>
>                 <artifactId>dom4j</artifactId>
>                 <version>2.1.3</version>
>             </dependency>
>             <dependency>
>                 <groupId>org.apache.logging.log4j</groupId>
>                 <artifactId>log4j-core</artifactId>
>                 <version>2.19.0</version>
>             </dependency>
>             <dependency>
>                 <groupId>org.apache.logging.log4j</groupId>
>                 <artifactId>log4j-slf4j2-impl</artifactId>
>                 <version>2.19.0</version>
>             </dependency>
>             
>             <dependency>
>                 <groupId>junit</groupId>
>                 <artifactId>junit</artifactId>
>                 <version>4.13.2</version>
>                 <scope>test</scope>
>             </dependency>
>             <dependency>
>                 <groupId>jaxen</groupId>
>                 <artifactId>jaxen</artifactId>
>                 <version>1.2.0</version>
>             </dependency>
>         </dependencies>
>         <properties>
>             <maven.compiler.source>17</maven.compiler.source>
>             <maven.compiler.target>17</maven.compiler.target>
>             <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
>         </properties>
>     
>     </project>

>     package org.myspringframework.core;
>     
>     import java.io.InputStream;
>     import java.lang.reflect.Constructor;
>     import java.util.HashMap;
>     import java.util.List;
>     import java.util.Map;
>     
>     import org.dom4j.Document;
>     import org.dom4j.DocumentException;
>     import org.dom4j.Element;
>     import org.dom4j.Node;
>     import org.dom4j.io.SAXReader;
>     import org.slf4j.Logger;
>     import org.slf4j.LoggerFactory;
>     
>     public class ClassPathXmlApplicationContext implements ApplicationContext
>     {
>         private static final Logger logger = LoggerFactory.getLogger(ClassPathXmlApplicationContext.class);
>         private Map<String,Object> singletonObjects = new HashMap<>();
>         //解析mySpring配置文件,初始化所有的Bean,配置文件应当放在类路径下
>         public ClassPathXmlApplicationContext(String configLocation)
>         {
>             try
>             {
>                 //这是DOM4J解析XML的核心对象
>                 SAXReader saxReader = new SAXReader();
>                 //用类加载器获取系统类加载器,系统类加载器能获取类路径当中的资源,再以流的形式获取资源
>                 InputStream in = ClassLoader.getSystemClassLoader().getResourceAsStream(configLocation);
>                 Document document = saxReader.read(in);
>                 //当XML文件有很多同名标签,如果需要获取就用//后加名字即可
>                 List<Node> list = document.selectNodes("//bean");
>     //            遍历Bean标签
>                 list.forEach(node -> {
>                     try
>                     {
>                         //向下转型,方法更丰富
>                         Element beanEle = (Element) node;
>                         //获取ID
>                         String id = beanEle.attributeValue("id");
>                         //获取className
>                         String className = beanEle.attributeValue("class");
>                         logger.info(id + className);
>                         //通过反射机制创建对象,将其放到Map集合中曝光
>                         Class clazz = Class.forName(className);
>                         Constructor constructor = clazz.getDeclaredConstructor();
>                         //bean对象
>                         Object o = constructor.newInstance();
>                         singletonObjects.put(id,o);
>                         logger.info(singletonObjects.toString());
>                     }
>                     catch(Exception e)
>                     {
>                         e.printStackTrace();
>                     }
>     
>                 });
>                 //解析XML文件,实例化Bean,把Bean放到map容器中
>                 //getBean方法就变成了调用get()方法,并传入一个key即Bean的ID即可
>             }
>             catch (DocumentException e)
>             {
>                 e.printStackTrace();
>             }
>         }
>         @Override
>         public Object getBean(String name) {
>             return singletonObjects.get(name);
>         }
>     }
> 
>     package org.myspringframework.core;
>     
>     import java.io.InputStream;
>     import java.lang.reflect.Constructor;
>     import java.util.HashMap;
>     import java.util.List;
>     import java.util.Map;
>     
>     import org.dom4j.Document;
>     import org.dom4j.DocumentException;
>     import org.dom4j.Element;
>     import org.dom4j.Node;
>     import org.dom4j.io.SAXReader;
>     import org.slf4j.Logger;
>     import org.slf4j.LoggerFactory;
>     
>     public class ClassPathXmlApplicationContext implements ApplicationContext
>     {
>         private static final Logger logger = LoggerFactory.getLogger(ClassPathXmlApplicationContext.class);
>         private Map<String,Object> singletonObjects = new HashMap<>();
>         //解析mySpring配置文件,初始化所有的Bean,配置文件应当放在类路径下
>         public ClassPathXmlApplicationContext(String configLocation)
>         {
>             try
>             {
>                 //这是DOM4J解析XML的核心对象
>                 SAXReader saxReader = new SAXReader();
>                 //用类加载器获取系统类加载器,系统类加载器能获取类路径当中的资源,再以流的形式获取资源
>                 InputStream in = ClassLoader.getSystemClassLoader().getResourceAsStream(configLocation);
>                 Document document = saxReader.read(in);
>                 //当XML文件有很多同名标签,如果需要获取就用//后加名字即可
>                 List<Node> list = document.selectNodes("//bean");
>     //            遍历Bean标签
>                 list.forEach(node -> {
>                     try
>                     {
>                         //向下转型,方法更丰富
>                         Element beanEle = (Element) node;
>                         //获取ID
>                         String id = beanEle.attributeValue("id");
>                         //获取className
>                         String className = beanEle.attributeValue("class");
>                         logger.info(id + className);
>                         //通过反射机制创建对象,将其放到Map集合中曝光
>                         Class clazz = Class.forName(className);
>                         Constructor constructor = clazz.getDeclaredConstructor();
>                         //bean对象
>                         Object o = constructor.newInstance();
>                         singletonObjects.put(id,o);
>                         logger.info(singletonObjects.toString());
>                     }
>                     catch(Exception e)
>                     {
>                         e.printStackTrace();
>                     }
>     
>                 });
>                 //解析XML文件,实例化Bean,把Bean放到map容器中
>                 //getBean方法就变成了调用get()方法,并传入一个key即Bean的ID即可
>             }
>             catch (DocumentException e)
>             {
>                 e.printStackTrace();
>             }
>         }
>         @Override
>         public Object getBean(String name) {
>             return singletonObjects.get(name);
>         }
>     }

>     package org.myspringframework.core;
>     
>     public interface ApplicationContext
>     {
>         //根据Bean的名称获取对应的单例Bean对象
>         Object getBean(String name);
>     }
> 
>     package org.myspringframework.core;
>     
>     public interface ApplicationContext
>     {
>         //根据Bean的名称获取对应的单例Bean对象
>         Object getBean(String name);
>     }

>     <?xml version="1.0" encoding="UTF-8"?>
>     
>     <beans>
>         <bean id="user" class="com.powernode.myspring.bean.User">
>             <property name="name" value="Jack"></property>
>             <property name="age" value="30"></property>
>         </bean>
>         <bean id="userDaoBean" class="com.powernode.myspring.bean.UserDao">
>         </bean>
>         <bean id="userService" class="com.powernode.myspring.bean.UserService">
>             <property name="userDao" ref="userDaoBean"></property>
>         </bean>
>     </beans>
> 
>     <?xml version="1.0" encoding="UTF-8"?>
>     
>     <beans>
>         <bean id="user" class="com.powernode.myspring.bean.User">
>             <property name="name" value="Jack"></property>
>             <property name="age" value="30"></property>
>         </bean>
>         <bean id="userDaoBean" class="com.powernode.myspring.bean.UserDao">
>         </bean>
>         <bean id="userService" class="com.powernode.myspring.bean.UserService">
>             <property name="userDao" ref="userDaoBean"></property>
>         </bean>
>     </beans>

>     package com.powernode.myspring.bean;
>     
>     public class UserService
>     {
>         private UserDao userDao;
>     
>         public void setUserDao(UserDao userDao) {
>             this.userDao = userDao;
>         }
>     
>         public void save()
>         {
>             userDao.insert();
>         }
>     }
> 
>     package com.powernode.myspring.bean;
>     
>     public class UserService
>     {
>         private UserDao userDao;
>     
>         public void setUserDao(UserDao userDao) {
>             this.userDao = userDao;
>         }
>     
>         public void save()
>         {
>             userDao.insert();
>         }
>     }

>     package com.powernode.myspring.bean;
>     
>     import org.slf4j.Logger;
>     import org.slf4j.LoggerFactory;
>     
>     public class UserDao
>     {
>         private static final Logger logger = LoggerFactory.getLogger(UserDao.class);
>         public void insert()
>         {
>             logger.info("mysql数据库正在保存用户信息");
>         }
>     }
> 
>     package com.powernode.myspring.bean;
>     
>     import org.slf4j.Logger;
>     import org.slf4j.LoggerFactory;
>     
>     public class UserDao
>     {
>         private static final Logger logger = LoggerFactory.getLogger(UserDao.class);
>         public void insert()
>         {
>             logger.info("mysql数据库正在保存用户信息");
>         }
>     }

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

>     package com.powernode.myspring.test;
>     
>     import org.junit.Test;
>     import org.myspringframework.core.ApplicationContext;
>     import org.myspringframework.core.ClassPathXmlApplicationContext;
>     
>     public class MySpringTest
>     {
>         @Test
>         public void Test()
>         {
>             ApplicationContext applicationContext = new ClassPathXmlApplicationContext("myspring.xml");
>     
>         }
>     }
> 
>     package com.powernode.myspring.test;
>     
>     import org.junit.Test;
>     import org.myspringframework.core.ApplicationContext;
>     import org.myspringframework.core.ClassPathXmlApplicationContext;
>     
>     public class MySpringTest
>     {
>         @Test
>         public void Test()
>         {
>             ApplicationContext applicationContext = new ClassPathXmlApplicationContext("myspring.xml");
>     
>         }
>     }