@Compenent,@Autowired,@PostConstruct自实现

时间  2019-11-13
标签 compenent autowired postconstruct 实现 繁體版
原文   原文链接

原本是想为安卓开发一套能够依赖注入的标签，可是发现安卓很难找到选定包内的java或者class文件。因此只能当作学习参考了，全套代码以下java

package com.guanjian.annotion;

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

/**
 * Created by Administrator on 2018-06-11.
 */
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Autowired {
}
package com.guanjian.annotion;

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

/**
 * Created by Administrator on 2018-06-11.
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Component {
}
package com.guanjian.annotion;

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

/**
 * Created by Administrator on 2018-06-11.
 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface PostConstruct {
}
package com.guanjian.util;

import com.guanjian.utils.StringUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import java.net.JarURLConnection;
import java.net.URL;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

/**
 * 类操做工具类
 * Created by Administrator on 2018-06-11.
 */
public final class ClassUtil {
    private static final Logger LOGGER = LoggerFactory.getLogger(ClassUtil.class);

    /**
     * 获取类加载器
     * @return
     */
    public static ClassLoader getClassLoader() {
        return Thread.currentThread().getContextClassLoader();
    }

    /**
     * 加载类
     * @param className
     * @param isInitialized
     * @return
     */
    public static Class<?> loadClass(String className,boolean isInitialized) {
        Class<?> cls;
        try {
            cls = Class.forName(className,isInitialized,getClassLoader());
        } catch (ClassNotFoundException e) {
            LOGGER.error("load class failure",e);
            throw new RuntimeException(e);
        }
        return cls;
    }

    /**
     * 获取制定包名下的全部类
     * @param packageName
     * @return
     */
    public static Set<Class<?>> getClassSet(String packageName) {
        Set<Class<?>> classSet = new HashSet<Class<?>>();
        try {
            Enumeration<URL> urls = getClassLoader().getResources(packageName.replace(".","/"));
            while (urls.hasMoreElements()) {
                URL url = urls.nextElement();
                if (url != null) {
                    String protocol = url.getProtocol();
                    if (protocol.equals("file")) {
                        String packagePath = url.getPath().replaceAll("%20"," ");
                        addClass(classSet,packagePath,packageName);
                    }else if (protocol.equals("jar")) {
                        JarURLConnection jarURLConnection = (JarURLConnection)url.openConnection();
                        if (jarURLConnection != null) {
                            JarFile jarFile = jarURLConnection.getJarFile();
                            if (jarFile != null) {
                                Enumeration<JarEntry> jarEntries = jarFile.entries();
                                while (jarEntries.hasMoreElements()) {
                                    JarEntry jarEntry = jarEntries.nextElement();
                                    String jarEntryName = jarEntry.getName();
                                    if (jarEntryName.endsWith(".class")) {
                                        String className = jarEntryName.substring(0,jarEntryName.lastIndexOf(".")).replaceAll("/",".");
                                        doAddClass(classSet,className);
                                    }
                                }
                            }
                        }
                    }
                }
            }
        } catch (Exception e) {
            LOGGER.error("get class set failure",e);
            throw new RuntimeException(e);
        }
        return classSet;
    }

    private static void addClass(Set<Class<?>> classSet, String packagePath, final String packageName) {
        File[] files = new File(packagePath).listFiles(new FileFilter() {
            public boolean accept(File pathname) {
                return (pathname.isFile() && pathname.getName().endsWith(".class")) || pathname.isDirectory();
            }
        });
        for (File file:files) {
            String fileName = file.getName();
            if (file.isFile()) {
                String className = fileName.substring(0,fileName.lastIndexOf("."));
                if (StringUtil.isNotEmpty(packagePath)) {
                    className = packageName + "." + className;
                }
                doAddClass(classSet,className);
            }else {
                String subPackagePath = fileName;
                if (StringUtil.isNotEmpty(packagePath)) {
                    subPackagePath = packagePath + "/" +subPackagePath;
                }
                String subPackageName = fileName;
                if (StringUtil.isNotEmpty(packageName)) {
                    subPackageName = packageName + "." +subPackageName;
                }
                addClass(classSet,subPackagePath,subPackageName);
            }
        }
    }
    private static void doAddClass(Set<Class<?>> classSet,String className) {
        Class<?> cls = loadClass(className,false);
        classSet.add(cls);
    }
}
package com.guanjian.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.lang.reflect.Field;

/**
 * 反射工具类
 * Created by Administrator on 2018-06-11.
 */
public final class ReflectionUtil {
    private static final Logger LOGGER = LoggerFactory.getLogger(ReflectionUtil.class);

    /**
     * 建立实例
     * @param cls
     * @return
     */
    public static Object newInstance(Class<?> cls) {
        Object instance;
        try {
            instance = cls.newInstance();
        } catch (Exception e) {
            LOGGER.error("new instance failure",e);
            throw new RuntimeException(e);
        }
        return instance;
    }

    /**
     * 设置成员变量值
     * @param obj
     * @param field
     * @param value
     */
    public static void setField(Object obj, Field field,Object value) {
        try {
            field.setAccessible(true);
            field.set(obj,value);
        } catch (IllegalAccessException e) {
            LOGGER.error("set field failure",e);
            throw new RuntimeException(e);
        }
    }
}
package com.guanjian.util;

import com.guanjian.annotion.Component;

import java.util.HashSet;
import java.util.Set;

/**
 * 类操做助手类
 * Created by Administrator on 2018-06-11.
 */
public final class ClassHelper {
    /**
     * 定义类集合(用于存放所加载的类)
     * @param basePackage
     */
    private static  Set<Class<?>> CLASS_SET;

    /**
     * 扫描全部的包，获取类集合放入CLASS_SET
     * @param basePackage
     */
    public static void setClassSet(String basePackage) {
        CLASS_SET = ClassUtil.getClassSet(basePackage);
    }

    /**
     * 获取应用包名下的全部类
     * @return
     */
    public static Set<Class<?>> getClassSet() {
        return CLASS_SET;
    }

    /**
     * 获取应用包名下全部Comonent类
     * @return
     */
    public static Set<Class<?>> getComponentClassSet() {
        Set<Class<?>> classSet = new HashSet<Class<?>>();
        for (Class<?> cls:CLASS_SET) {
            if (cls.isAnnotationPresent(Component.class)) {
                classSet.add(cls);
            }
        }
        return classSet;
    }

    /**
     * 获取应用包名下全部Bean类
     * @return
     */
    public static Set<Class<?>> getBeanClassSet() {
        Set<Class<?>> beanClassSet = new HashSet<Class<?>>();
        beanClassSet.addAll(getComponentClassSet());
        return beanClassSet;
    }
}
package com.guanjian.util;

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

/**
 * Bean助手类
 * Created by Administrator on 2018-06-11.
 */
public final class BeanHelper {
    /**
     * 定义Bean映射(用于存放Bean类与Bean实例的映射关系)
     */
    private static final Map<Class<?>,Object> BEAN_MAP = new HashMap<Class<?>, Object>();

    /**
     * 获取全部的映射关系
     */
    public static void setBeanMap() {
        Set<Class<?>> beanClassSet = ClassHelper.getBeanClassSet();
        for (Class<?> beanClass:beanClassSet) {
            Object obj = ReflectionUtil.newInstance(beanClass);
            BEAN_MAP.put(beanClass,obj);
        }
    }

    /**
     * 获取Bean映射
     * @return
     */
    public static Map<Class<?>,Object> getBeanMap() {
        return BEAN_MAP;
    }

    /**
     * 获取Bean实例
     * @param cls
     * @param <T>
     * @return
     */
    public static <T> T getBean(Class<T> cls) {
        if (!BEAN_MAP.containsKey(cls)) {
            throw new RuntimeException("Can not get bean by class:" + cls);
        }
        return (T)BEAN_MAP.get(cls);
    }
}
package com.guanjian.util;

import com.guanjian.annotion.Autowired;
import com.guanjian.annotion.PostConstruct;
import com.guanjian.utils.ArrayUtil;
import com.guanjian.utils.CollectionUtil;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Map;

/**
 * Created by Administrator on 2018-06-11.
 */
public final class IocHelper {
    public static void ioc(){
        //获取全部的Bean类与Bean实例之间的映射关系
        Map<Class<?>,Object> beanMap = BeanHelper.getBeanMap();
        if (CollectionUtil.isNotEmpty(beanMap)) {
            //遍历Bean Map
            for (Map.Entry<Class<?>,Object> beanEntry:beanMap.entrySet()) {
                //从BeanMap中获取Bean类与Bean实例
                Class<?> beanClass = beanEntry.getKey();
                Object beanInstance = beanEntry.getValue();
                //获取Bean类定义的全部成员变量
                Field[] beanFields = beanClass.getDeclaredFields();
                if (ArrayUtil.isNotEmpty(beanFields)) {
                    //遍历Bean Field
                    for (Field beanField:beanFields) {
                        //判断当前Bean Field是否带有Autowired注解
                        if (beanField.isAnnotationPresent(Autowired.class)) {
                            //在Bean Map中获取Bean Field对应的实例
                            Class<?> beanFieldClass = beanField.getType();
                            Object beanFieldInstance = beanMap.get(beanFieldClass);
                            if (beanFieldInstance != null) {
                                //经过反射初始化BeanField的值
                                ReflectionUtil.setField(beanInstance,beanField,beanFieldInstance);
                            }
                        }
                    }
                }
                Method[] beanMethods = beanClass.getMethods();
                if (ArrayUtil.isNotEmpty(beanMethods)) {
                    //遍历method
                    for (Method method:beanMethods) {
                        //判断当前注解是否有PostConstruct注解
                        if (method.isAnnotationPresent(PostConstruct.class)) {
                            try {
                                //执行该方法
                                method.invoke(beanInstance,null);
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            }
        }
    }
}
package com.guanjian.manage;

import com.guanjian.util.BeanHelper;
import com.guanjian.util.ClassHelper;
import com.guanjian.util.IocHelper;

/**
 * Created by Administrator on 2018-06-11.
 */
public class Manager {
    public static Object getBean(Class<?> beanClass) {
        return BeanHelper.getBean(beanClass);
    }
    public static void scanAndImp(String basePackage) {
        ClassHelper.setClassSet(basePackage);
        BeanHelper.setBeanMap();
        IocHelper.ioc();
    }
}

测试代码工具

package com.guanjian.test.compent;

import com.guanjian.annotion.Component;
import com.guanjian.annotion.PostConstruct;

/**
 * Created by Administrator on 2018-06-11.
 */
@Component
public class Test1 {
    private String hello;
    @PostConstruct
    public void init() {
        hello = "你好";
    }
    public void show() {
        System.out.println(hello);
    }
}
package com.guanjian.test.compent;

import com.guanjian.annotion.Autowired;
import com.guanjian.annotion.Component;

/**
 * Created by Administrator on 2018-06-11.
 */
@Component
public class Test2 {
    @Autowired
    private Test1 test1;
    public void show() {
        test1.show();
    }
}
package com.guanjian.test;

import com.guanjian.manage.Manager;
import com.guanjian.test.compent.Test2;

/**
 * Created by Administrator on 2018-06-11.
 */
public class Test {
    public static void main(String[] args) {
        Manager.scanAndImp("com.guanjian.test");
        Test2 test2 = (Test2)Manager.getBean(Test2.class);
        test2.show();
}
}
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