SpringIOC随笔（二）-仿写SpringIOC

分手后的思念是犯贱 2022-12-16 14:24 265阅读 0赞

# SpringIOC随笔（二）-仿写SpringIOC #

### 思路： ###

1.  定义一个beanFactor工厂接口，提供getBean方法，
2.  实现工厂，定义一个Bean容器，Map，为了实现线程安全，使用`private static Map<String, Object> beanMap = Collections.synchronizedMap(new HashMap<>());`
3.  初始化我们的bean容器，通过解析我们的xml配置文件`//beans/bean`创建出bean
4.  初始化完成bean容器后我们需要将bean之间的关系装配好（注入）
5.  然后实现getBean方法。

### 使用技术：dom4j解析xml，反射 ###

### 代码： ###

1.  pom
    
        <dependencies>
                <dependency>
                    <groupId>dom4j</groupId>
                    <artifactId>dom4j</artifactId>
                    <version>1.6.1</version>
                </dependency>
                <dependency>
                    <groupId>jaxen</groupId>
                    <artifactId>jaxen</artifactId>
                    <version>1.1.6</version>
                </dependency>
                <dependency>
                    <groupId>org.apache.commons</groupId>
                    <artifactId>commons-lang3</artifactId>
                    <version>3.4</version>
                </dependency>
                <dependency>
                    <groupId>commons-collections</groupId>
                    <artifactId>commons-collections</artifactId>
                    <version>3.2.1</version>
                </dependency>
                <dependency>
                    <groupId>junit</groupId>
                    <artifactId>junit</artifactId>
                    <version>4.12</version>
                    <scope>test</scope>
                </dependency>
            </dependencies>
2.  applicationContext.xml
    
        <?xml version="1.0" encoding="UTF-8" ?>
        <beans>
            <bean id="userDaoHibernate" class="com.fxyh.spring.dao.impl.UserDaoHibernateImpl" />
        
            <bean id="userDaoMybatis" class="com.fxyh.spring.dao.impl.UserDaoMybatisImpl"/>
        
            <bean id="userService" class="com.fxyh.spring.service.impl.UserServiceImpl">
                <property name="userDao" ref="userDaoMybatis" />
            </bean>
        </beans>
3.  Dom4jUtils
    
        public class Dom4jUtils {
              
        
            /**
             * @Author fengzhaoquan
             * @Description 获取XML文档。其实就是将xml文档读取到内存中，形成DOM树
             * @Date  
             * @Param 
             * @return 
             **/
            public static Document getDocument(String fileName){
              
                Document document = null;
                if(StringUtils.isBlank(fileName)){
              
                    throw new IllegalArgumentException("");
                }
                try {
              
                    SAXReader reader = new SAXReader();
                    document = reader.read(Dom4jUtils.class.getClassLoader().getResourceAsStream(fileName));
                } catch (DocumentException e) {
              
                    e.printStackTrace();
                }
                return document;
            }
        
        }
4.  BeanFactory接口
    
        public interface BeanFactory {
              
        
            /**
             * @Author fengzhaoquan
             * @Description 实现了该接口类型的对象
             * @Param clazz 接口类型的对象
             **/
            Object getBean(Class clazz);
        
            /**
             * @Author fengzhaoquan
             * @Description 获取className的对象（id）
             **/
            Object getBean(String className);
        }
5.  ClassPathXmlApplicationContext实现BeanFactory接口
    
        /**
         * @ClassName: ClassPathXmlApplicationContext
         * @description: BeanFactory的一个实现类
         * 1. 将xml中所有的bean标签创建出对象，然后放入容器中
         * 2. 对外提供了getBean方法，从而对于客户端而言可以很轻松的获取对象
         * @author: fengzhaoquan
         * @create: 2019-06-16 16:44
         * @Version 1.0
         **/
        public class ClassPathXmlApplicationContext implements BeanFactory {
              
        
            /**
             * @Author fengzhaoquan
             * @Description 配置文件中所有的bean都会放入beanMap中
             **/
            private static Map<String, Object> beanMap = Collections.synchronizedMap(new HashMap<>());
        
            public ClassPathXmlApplicationContext() {
              
                this("applicationContext.xml");
            }
        
            public ClassPathXmlApplicationContext(String fileName) {
              
                if (StringUtils.isBlank(fileName)) {
              
                    throw new IllegalArgumentException("");
                }
                try {
              
                    // 解析XML
                    // 初始化beanMap
                    initBeanMap(fileName);
                    // 将bean之间的关系装配好(注入)
                    injection(fileName);
                } catch (Exception e) {
              
                    e.printStackTrace();
                }
            }
        
            /**
             * @Author fengzhaoquan
             * @Description 将bean之间的关系装配好（注入）
             **/
            private void injection(String fileName) throws Exception {
              
                Document document = Dom4jUtils.getDocument(fileName);
                List<Element> propertyElementList = document.selectNodes("//beans/bean/property");
        
                if (CollectionUtils.isNotEmpty(propertyElementList)) {
              
                    for (Element propertyElement : propertyElementList) {
              
                        String name = propertyElement.attributeValue("name");
                        String refValue = propertyElement.attributeValue("ref");
        
                        //setXxx方法拼接
                        String methodName = "set" + name.substring(0, 1).toUpperCase() + name.substring(1);
        
                        //找到父元素，也是就要被注入的对象
                        Element beanElement = propertyElement.getParent();
                        String parentElementIdValue = beanElement.attributeValue("id");
                        if (beanMap.containsKey(parentElementIdValue) && beanMap.containsKey(refValue)){
              
                            Object targetObject = beanMap.get(parentElementIdValue);
                            Object parameterValue = beanMap.get(refValue);
                            Method method = targetObject.getClass().getDeclaredMethod(methodName, parameterValue.getClass().getInterfaces());
                            method.invoke(targetObject, parameterValue);
                        }
                    }
                }
        
            }
        
            /**
             * @Author fengzhaoquan
             * @Description 初始化beanMap
             **/
            private void initBeanMap(String fileName) throws ClassNotFoundException, IllegalAccessException, InstantiationException {
              
                Document document = Dom4jUtils.getDocument(fileName);
                //XPath
                List<Element> beanElementList = document.selectNodes("//beans/bean");
                if (CollectionUtils.isNotEmpty(beanElementList)) {
              
                    for (Element beanElement : beanElementList) {
              
                        String id = beanElement.attributeValue("id");
                        String beanClassName = beanElement.attributeValue("class");
                        beanMap.put(id, Class.forName(beanClassName).newInstance());
                    }
                }
            }
        
        
            @Override
            public Object getBean(Class clazz) {
              
                if(clazz == null){
              
                    throw new IllegalArgumentException("");
                }
                return beanMap.get(clazz.getSimpleName().substring(0,1).toLowerCase() + clazz.getSimpleName().substring(1));
            }
        
            @Override
            public Object getBean(String className) {
              
                if(StringUtils.isBlank(className)){
              
                    throw new IllegalArgumentException("");
                }
                return beanMap.get(className);
            }
        }
6.  Service，Dao，model代码：
    
        public class UserServiceImpl implements UserService {
              
        
            private UserDao userDao;
        
            public void setUserDao(UserDao userDao) {
              
                this.userDao = userDao;
            }
        
            @Override
            public void addUser(User user) {
              
                userDao.addUser(user);
            }
        }
        public class UserDaoHibernateImpl implements UserDao {
              
            @Override
            public void addUser(User user) {
              
                System.out.println("Hibernate add:" + user);
            }
        }
        public class UserDaoMybatisImpl implements UserDao {
              
            @Override
            public void addUser(User user) {
              
                System.out.println("Mybatis add:" + user);
            }
        }
        public class User implements Serializable {
              
        
            private static final long serialVersionUID = -5333671573596770181L;
            private String name;
            private String password;
        
            public String getName() {
              
                return name;
            }
        
            public void setName(String name) {
              
                this.name = name;
            }
        
            public String getPassword() {
              
                return password;
            }
        
            public void setPassword(String password) {
              
                this.password = password;
            }
        
            @Override
            public String toString() {
              
                return "User{" +
                        "name='" + name + '\'' +
                        ", password='" + password + '\'' +
                        '}';
            }
        }
7.  单元测试
    
        public class UserServiceImplTest {
              
        
            private BeanFactory factory;
        
            private UserService userService;
        
            @Before
            public void setUp() throws Exception {
              
                this.factory = new ClassPathXmlApplicationContext();
                this.userService = (UserService) this.factory.getBean(UserService.class);
            }
        
            @Test
            public void addUser() {
              
                User user = new User();
                user.setName("zhangsan");
                user.setPassword("123456");
                userService.addUser(user);
            }
        }

### 这是一个基本上可以说非常简陋的IOC，但是和Spring的原理是一样的。 ###