纯手写springIOC

Posted 2021-01-31 zgwjava

 大家好啊～ 那么今天来带大家写一下spring的ioc。

  其实也很简单，首先我们明白两点，java解析xml和java的反射机制，因为ioc就是主要是基于这两个来实现，今天只是简单的来大家实现下。

  废话不多说直接上代码。

  1.首先加入maven依赖我们这里用到的xml解析是dem4j，先看下项目结构吧。

  2.导入maven依赖

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <project xmlns="http://maven.apache.org/POM/4.0.0"
 3          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 5     <modelVersion>4.0.0</modelVersion>
 6 
 7     <groupId>com.gd</groupId>
 8     <artifactId>mySpringIOC</artifactId>
 9     <version>1.0-SNAPSHOT</version>
10     <packaging>jar</packaging>
11 
12     <dependencies>
13         <dependency>
14             <groupId>dom4j</groupId>
15             <artifactId>dom4j</artifactId>
16             <version>1.6.1</version>
17         </dependency>
18     </dependencies>
19 </project>

3.首先我们来看MyApplicationContext这个接口

package org.zgw.framework.spring.ioc;

/**
 * @DATA 2018-12-30 23:05
 * @Author zhangguowei  WeChat:17630376104
 * @Description TODO
 */
public interface MyApplicationContext {
    Object getBean(String beanId);

    Object getBean(Class clazz);
}

　　这个接口中有个两个getbBean();重栽的方法。这两个接口也就是ioc的id大家用过spring 的应该都知道，这里不过多的解释。

4.接着看我们的MyClassPathXmlApplicationContext这个实现类。

package org.zgw.framework.spring.ioc;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.zgw.framework.spring.ioc.model.BeanDefinition;
import org.zgw.framework.spring.ioc.model.PropertyDefinition;

import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * @DATA 2018-12-30 23:07
 * @Author zhangguowei  WeChat:17630376104
 * @Description TODO
 */
public class MyClassPathXmlApplicationContext implements MyApplicationContext {

    private Map<String, BeanDefinition> stringBeanDefinitionMap = new HashMap<String, BeanDefinition>();


    public MyClassPathXmlApplicationContext(String xmlName) {
        loadXml(xmlName);
    }

    private void loadXml(String xmlName) {
        SAXReader reader = new SAXReader();
                 //读取xml
        InputStream inputStream = Thread.currentThread().getContextClassLoader().getResourceAsStream(xmlName);
        try {
            Document document = reader.read(inputStream);
            // 获取标签
            Element element = document.getRootElement();
            System.out.println("根节点:" + element.getName());
            List<Element> elementList = element.elements();
            for (Element beanlist : elementList) {
                System.out.println("子节点:" + beanlist.getName() + "	" + beanlist.attributeValue("id") + "	" + beanlist.attributeValue("class"));

                BeanDefinition beanDefinition = new BeanDefinition();
                  //读取name的值
                beanDefinition.setName(beanlist.attributeValue("name"));
                  //读取class的值
                beanDefinition.setClassStr(beanlist.attributeValue("class"));


                List<Element> proList = beanlist.elements();
                for (Element element1 : proList) {
                    System.out.println(element1.getName() + "	" + element1.attributeValue("name") + "	" + element1.getText());
                    PropertyDefinition propertyDefinition = new PropertyDefinition();
                    propertyDefinition.setName(element1.attributeValue("name"));
                    propertyDefinition.setValue(element1.attributeValue("value"));
                    beanDefinition.getPropertyDefinitionMap().put(propertyDefinition.getName(), propertyDefinition);


                }
                stringBeanDefinitionMap.put(beanDefinition.getName(), beanDefinition);
            }

        } catch (DocumentException e) {
            e.printStackTrace();
        }

    }

    public Object getBean(String beanId) {
        BeanDefinition beanDefinition = stringBeanDefinitionMap.get(beanId);
        String clazzStr = beanDefinition.getClassStr();
        Object beanobj = null;
        try {
            Class clazz = Class.forName(clazzStr);
            beanobj = clazz.newInstance();
            // 给属性赋值
            Collection<PropertyDefinition> propertyDefinitions = beanDefinition.getPropertyDefinitionMap().values();
            for (PropertyDefinition propertyDefinition : propertyDefinitions) {
                String setterMethodStr = propertyDefinition.getName();
                //因为spring读的是他个set方法，一般set方法都为大写开头所以这里进行转换
                String firstChar = setterMethodStr.substring(0, 1).toUpperCase();
                setterMethodStr = "set" + firstChar + setterMethodStr.substring(1);
                System.out.println("-------- 拼接出来的set方法" + setterMethodStr);
               Method setMathod= clazz.getMethod(setterMethodStr,String.class);
               setMathod.invoke(beanobj,propertyDefinition.getValue());

            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        return beanobj;
    }

    public Object getBean(Class clazz) {
        return null;
    }
}

　　基本的注释我都写有，这些大家应该能看的懂。

5.还有一点就是两个实体的类，因为她们得对应spring的属性

package org.zgw.framework.spring.ioc.model;

import java.util.HashMap;
import java.util.Map;

/**
 * @DATA 2018-12-30 23:15
 * @Author zhangguowei  WeChat:17630376104
 * @Description TODO
 */
public class BeanDefinition {
    private String name;

    private String classStr;

    private Map<String, PropertyDefinition> propertyDefinitionMap = new HashMap<String, PropertyDefinition>();

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getClassStr() {
        return classStr;
    }

    public void setClassStr(String classStr) {
        this.classStr = classStr;
    }

    public Map<String, PropertyDefinition> getPropertyDefinitionMap() {
        return propertyDefinitionMap;
    }

    public void setPropertyDefinitionMap(Map<String, PropertyDefinition> propertyDefinitionMap) {
        this.propertyDefinitionMap = propertyDefinitionMap;
    }
}

　　

package org.zgw.framework.spring.ioc.model;

/**
 * @DATA 2018-12-30 23:17
 * @Author zhangguowei  WeChat:17630376104
 * @Description TODO
 */
public class PropertyDefinition
{
    private String name;
    private String value;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }
}

　　这个只是基于xml的ioc，直接上代码，可以拷贝走尝试下，方便大家理解。后续还有ioc的注解方式实现。