手写SpringIOC容器框架

1.使用xml方式注入对象

导入依赖：

<!-- https://mvnrepository.com/artifact/dom4j/dom4j -->
<dependency>
    <groupId>dom4j</groupId>
    <artifactId>dom4j</artifactId>
    <version>1.6.1</version>
</dependency>

/**
 * Created by yz on 2018/6/3.
 */
public interface OrderService {
    public void addOrder();
}

/**
 * Created by yz on 2018/6/3.
 */
//@ExtService
public class OrderServiceImpl implements OrderService {
    @Override
    public void addOrder() {
        System.out.println("使用Java反射机制初始化对象...");
    }
}

spring.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">

    <bean id="orderService" class="com.yz.ioc.service.Impl.OrderServiceImpl"/>

</beans>

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.springframework.util.StringUtils;

import java.io.InputStream;
import java.util.List;

/**
 * 自定义spring容器框架 xml方式实现
 * Created by yz on 2018/6/3.
 */
public class ExtClassPathXmlApplicationContext {

    // xml读取路径地址
     private String xmlPath;

    public ExtClassPathXmlApplicationContext(String xmlPath) {
        this.xmlPath = xmlPath;
    }

    public Object getBean(String beanId) throws Exception {
        if(StringUtils.isEmpty(beanId)){
            return new Exception("bendId不能为空");
        }
        // 1.解析xml,获取所有bean节点信息
        List<Element> readerxml = readeXml(xmlPath);
        // 2.使用方法参数bend id查找配置文件中bean节点的id信息是否一致。
        if(readerxml == null || readerxml.isEmpty()){
            return new Exception("配置文件中，没有配置bean信息");
        }
        String className = findByElementClass(readerxml, beanId);
        if(StringUtils.isEmpty(className)){
            return new Exception("该bean对象没有配置class地址");
        }
        // 3.获取class信息地址，使用反射机制初始化
        return newInstance(className);
    }

    // 重构
    public String findByElementClass(List<Element> readerxml,String beanId) throws Exception {
        for (Element element : readerxml) {
            // 获取属性信息
            String xmlbeanId = element.attributeValue("id");
            if(StringUtils.isEmpty(xmlbeanId)){
                continue;
            }
            if(xmlbeanId.equals(beanId)){
                String xmlClassPath = element.attributeValue("class");
                return xmlClassPath;
            }
        }
        return null;
    }

    // 根据路径通过反射机制获取对象
    public Object newInstance(String className) throws Exception {
        Class<?> classInfo = Class.forName(className);
        return classInfo.getDeclaredConstructor().newInstance();
    }

    // 解析xml
    public List<Element> readeXml(String xmlPath) throws DocumentException {
        // 1.解析xml信息
        SAXReader saxReader = new SAXReader();
        Document document = saxReader.read(getResourcesAsStream(xmlPath));
        // 2.读取节点下所有的子节点
        Element rootElement = document.getRootElement();
        // 3.获取根节点下所有的子节点
        List<Element> elements = rootElement.elements();
        return elements;
    }

    // 获取当前上下文
    public InputStream getResourcesAsStream(String xmlPath){
        InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream(xmlPath);
        return inputStream;
    }

}

import com.yz.ioc.ExtClassPathXmlApplicationContext;
import com.yz.ioc.service.OrderService;

/**
 * 测试ioc代码
 * Created by yz on 2018/6/3.
 */
public class IOCTest {
    public static void main(String[] args) throws Exception {
        ExtClassPathXmlApplicationContext context = new ExtClassPathXmlApplicationContext("spring.xml");
        OrderService orderService = (OrderService) context.getBean("orderService");
        orderService.addOrder();
    }
}

2.使用注解方式注入对象 AOP IOC实现

spring.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"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    <!--使用自定义注解方式，扫包范围-->
    <context:component-scan base-package="com.yz.ioc"/>

</beans>

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * 自定义@Service注解 注入bean容器
 */
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface ExtService {
}

import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * 自定义@Resource注解 注入bean容器
 */
@Target({TYPE, FIELD, METHOD})
@Retention(RUNTIME)
public @interface ExtResource {
}

/**
 * Created by yz on 2018/6/3.
 */
public interface OrderService {
    void addOrder();
}

/**
 * Created by yz on 2018/6/3.
 */
@ExtService
public class OrderServiceImpl implements OrderService {
    @Override
    public void addOrder() {
        System.out.println("使用注解方式依赖注入...");
    }
}

/**
 * Created by yz on 2018/6/3.
 */
public interface UserService {
    void add();
}

import com.yz.ioc.annotation.ExtResource;
import com.yz.ioc.annotation.ExtService;
import com.yz.ioc.service.OrderService;
import com.yz.ioc.service.UserService;

/**
 * Created by yz on 2018/6/3.
 */
@ExtService
public class UserServiceImpl implements UserService {

    @ExtResource
    private OrderService orderService;

    @Override
    public void add(){
        orderService.addOrder();
    }

}

import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

/**
 * 类相关的工具类
 * Created by yz on 2018/6/3.
 */
public class ClassUtil {

    /**
     * 从包package中获取所有的Class
     * @param packageName
     * @return
     */
    public static List<Class<?>> getClasses(String packageName){

        //第一个class类的集合
        List<Class<?>> classes = new ArrayList<Class<?>>();
        //是否循环迭代
        boolean recursive = true;
        //获取包的名字 并进行替换
        String packageDirName = packageName.replace('.', '/');
        //定义一个枚举的集合 并进行循环来处理这个目录下的things
        Enumeration<URL> dirs;
        try {
            dirs = Thread.currentThread().getContextClassLoader().getResources(packageDirName);
            //循环迭代下去
            while (dirs.hasMoreElements()){
                //获取下一个元素
                URL url = dirs.nextElement();
                //得到协议的名称
                String protocol = url.getProtocol();
                //如果是以文件的形式保存在服务器上
                if ("file".equals(protocol)) {
                    //获取包的物理路径
                    String filePath = URLDecoder.decode(url.getFile(), "UTF-8");
                    //以文件的方式扫描整个包下的文件 并添加到集合中
                    findAndAddClassesInPackageByFile(packageName, filePath, recursive, classes);
                } else if ("jar".equals(protocol)){
                    //如果是jar包文件
                    //定义一个JarFile
                    JarFile jar;
                    try {
                        //获取jar
                        jar = ((JarURLConnection) url.openConnection()).getJarFile();
                        //从此jar包 得到一个枚举类
                        Enumeration<JarEntry> entries = jar.entries();
                        //同样的进行循环迭代
                        while (entries.hasMoreElements()) {
                            //获取jar里的一个实体 可以是目录 和一些jar包里的其他文件 如META-INF等文件
                            JarEntry entry = entries.nextElement();
                            String name = entry.getName();
                            //如果是以/开头的
                            if (name.charAt(0) == '/') {
                                //获取后面的字符串
                                name = name.substring(1);
                            }
                            //如果前半部分和定义的包名相同
                            if (name.startsWith(packageDirName)) {
                                int idx = name.lastIndexOf('/');
                                //如果以"/"结尾 是一个包
                                if (idx != -1) {
                                    //获取包名 把"/"替换成"."
                                    packageName = name.substring(0, idx).replace('/', '.');
                                }
                                //如果可以迭代下去 并且是一个包
                                if ((idx != -1) || recursive){
                                    //如果是一个.class文件 而且不是目录
                                    if (name.endsWith(".class") && !entry.isDirectory()) {
                                        //去掉后面的".class" 获取真正的类名
                                        String className = name.substring(packageName.length() + 1, name.length() - 6);
                                        try {
                                            //添加到classes
                                            classes.add(Class.forName(packageName + '.' + className));
                                        } catch (ClassNotFoundException e) {
                                            e.printStackTrace();
                                        }
                                    }
                                }
                            }
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        return classes;
    }

    /**
     * 以文件的形式来获取包下的所有Class
     * @param packageName
     * @param packagePath
     * @param recursive
     * @param classes
     */
    public static void findAndAddClassesInPackageByFile(String packageName, String packagePath, final boolean recursive, List<Class<?>> classes){
        //获取此包的目录 建立一个File
        File dir = new File(packagePath);
        //如果不存在或者 也不是目录就直接返回
        if (!dir.exists() || !dir.isDirectory()) {
            return;
        }
        //如果存在 就获取包下的所有文件 包括目录
        File[] dirfiles = dir.listFiles(new FileFilter() {
            //自定义过滤规则 如果可以循环(包含子目录) 或则是以.class结尾的文件(编译好的java类文件)
            public boolean accept(File file) {
                return (recursive && file.isDirectory()) || (file.getName().endsWith(".class"));
            }
        });
        //循环所有文件
        for (File file : dirfiles) {
            //如果是目录 则继续扫描
            if (file.isDirectory()) {
                findAndAddClassesInPackageByFile(packageName + "." + file.getName(),
                        file.getAbsolutePath(),
                        recursive,
                        classes);
            }
            else {
                //如果是java类文件 去掉后面的.class 只留下类名
                String className = file.getName().substring(0, file.getName().length() - 6);
                try {
                    //添加到集合中去
                    classes.add(Class.forName(packageName + '.' + className));
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

import com.yz.ioc.annotation.ExtResource;
import com.yz.ioc.annotation.ExtService;
import com.yz.ioc.uitl.ClassUtil;
import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.springframework.util.StringUtils;

import java.io.InputStream;
import java.lang.reflect.Field;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 自定义spring容器框架 注解方式实现
 * Created by yz on 2018/6/3.
 */
public class ExtClassPathXmlApplicationContext {

    // 定义springbean容器
    private ConcurrentHashMap<String,Object> beans;

    // 扫包的范围
    private String packageName;

    public ExtClassPathXmlApplicationContext(String xmlPath) throws Exception {
        // 初始化参数
        beans = new ConcurrentHashMap<>();
        this.packageName = getPackageName(xmlPath);
        initBeans();
        initEntryField();
    }

    // 初始化属性
    private void initEntryField() throws Exception {
        // 1.遍历所有bena容器对象
        for (Map.Entry<String, Object> entry : beans.entrySet()) {
            // 2.判断属性上面是否有加注解
            Object object = entry.getValue();
            inversionOfControl(object);
        }
    }

    public Object getBean(String beanId) throws Exception {
        System.out.println(beanId);
        if(StringUtils.isEmpty(beanId)){
            throw new Exception("beanId参数不能为空");
        }
        // 从spring容器获取bean
        Object object = beans.get(beanId);
        return object;
    }

    // 根据路径通过反射机制获取对象
    public Object newInstance(Class<?> classInfo) throws Exception {
        return classInfo.getDeclaredConstructor().newInstance();
    }

    // 初始化对象
    public void initBeans() throws Exception {
        // 1.使用Java的反射机制扫包，获取当前包下所有的类
        List<Class<?>> classes = ClassUtil.getClasses(packageName);
        // 2.判断类上是否存在注入bean的注解
        ConcurrentHashMap<String, Object> classIsAnnotation = findClassIsAnnotation(classes);
        if(classIsAnnotation == null || classIsAnnotation.isEmpty()){
            throw new Exception("该包下没有任何类加上注解");
        }
    }

    // 判断类上是否存在注入bean的注解
    public ConcurrentHashMap<String,Object> findClassIsAnnotation(List<Class<?>> classes) throws Exception {
        for (Class<?> classInfo : classes) {
            // 判断类上是否有注解
            ExtService annotation = classInfo.getAnnotation(ExtService.class);
            if(annotation !=null){
                // 获取当前类名，beanid 默认类名小写
                String className = classInfo.getSimpleName();
                String beanId = toLowerCaseFirstOne(className);
                // 通过反射机制创建对象
                Object newInstance = newInstance(classInfo);
                beans.put(beanId,newInstance);
                continue;
            }
        }
        return beans;
    }

    //首字母转小写
    public static String toLowerCaseFirstOne(String s){
        if(Character.isLowerCase(s.charAt(0)))
            return s;
        else
            return (new StringBuilder())
                    .append(Character.toLowerCase(s.charAt(0)))
                    .append(s.substring(1)).toString();
    }

    // 读取xml中配置的包路径
    public String getPackageName(String xmlPath) throws Exception {
        SAXReader saxReader = new SAXReader();
        // 读取xml文件
        Document document = saxReader.read(getResourcesAsStream(xmlPath));
        // 读取节点
        Element rootElement = document.getRootElement();
        // 获取根节点下所有的子节点
        List<Element> elements = rootElement.elements();
        for (Element element : elements) {
            if(element.getName().equals("component-scan")){
                // 获取扫包路径
                Attribute attribute = element.attribute("base-package");
                return attribute.getText();
            }
        }
        return null;
    }

    public InputStream getResourcesAsStream(String xmlPath){
        InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream(xmlPath);
        return inputStream;
    }

    // 依赖注入
    public void inversionOfControl(Object object) throws Exception {
        // 依赖注入实现原理
        // 1.使用反射机制，获取当前类的所有属性
        Class<?> classInfo = object.getClass();
        Field[] fileds = classInfo.getDeclaredFields();
        // 2.判断当前类属性是否存在注解
        for (Field filed : fileds) {
            // 3.默认使用属性名称，查找bean容器对象
            ExtResource extResource = filed.getAnnotation(ExtResource.class);
            if(extResource !=null){
                // 获取属性名称
                String beanId = filed.getName();
                Object bean = getBean(beanId+"Impl");
                if(bean != null){
                    // 允许访问私有属性
                    filed.setAccessible(true);
                    // 属性赋值
                    filed.set(object,bean);
                }
            }
        }
    }

}

/**
 * Created by yz on 2018/6/3.
 */
public class IOCTest {
    public static void main(String[] args) throws Exception {
        ExtClassPathXmlApplicationContext context = new ExtClassPathXmlApplicationContext("spring.xml");
//        OrderService orderService = (OrderService) context.getBean("orderServiceImpl");
//        orderService.addOrder();
        UserService userService = (UserService) context.getBean("userServiceImpl");
        userService.add();
    }
}