使用java反射，自定义springMvc简单案例

缺乏、安全感 2022-05-12 02:04 192阅读 0赞

目前javaWeb开发领域，SpringMvc已经是绝大部分中小公司必选框架，那么springMvc是如何实现的呢。这里通过一个简单的小案例来演示一下。

首先看一下案例的结构图

![70][]

目前springBoot项目比较流行，这里新建一个springBoot项目，先引入项目依赖

<?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>com.example</groupId>
        <artifactId>refect</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <packaging>jar</packaging>
    
        <name>refect</name>
        <description>Demo project for Spring Boot</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.5.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <properties>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
            <java.version>1.8</java.version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    
    
    </project>

1、新建AopMethod注解，这个注解可以理解为RequestMapping

package com.example.refect.aop.core;
    
    
    import java.lang.annotation.*;
    
    
    /**
     * 方法注解，这里类似RequestMapping
     */
    @Documented
    @Target(ElementType.METHOD)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface AopMethod {
    
        String value() default "";
    }

2、新建拦截器接口AopIntercepter，这里可以理解为SpringMvc拦截器

package com.example.refect.aop.core;
    
    
    /**
     * 拦截器
     */
    public abstract  class AopIntercepter {
    
    
        abstract void before();
    
    
        abstract void after();
    }

3、新建拦截器实现类AopIntercepterImp

package com.example.refect.aop.core;
    
    
    /**
     * 拦截器实现
     */
    public class AopIntercepterImp extends AopIntercepter {
    
    
        @Override
        public void before() {
            System.out.println("调用前执行：before");
        }
    
    
        @Override
        public void after() {
            System.out.println("调用后执行：after");
        }
    }

4、新建aop核心接口 AopInter

package com.example.refect.aop.core;
    
    
    import java.lang.reflect.Method;
    import java.util.List;
    
    /**
     * aop核心接口
     */
    public interface AopInter {
    
        List<Method> getMethods(Class<?> annotation, String[] packagePath);
    
    
        void invoke(Class<? extends AopIntercepter> clazz, Method method,Object args);
    
    
    }

5、新建核心接口实现类AopCore

package com.example.refect.aop.core;
    
    
    import org.springframework.util.StringUtils;
    
    import java.io.File;
    import java.io.IOException;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    import java.net.URL;
    import java.net.URLDecoder;
    import java.util.*;
    
    
    /**
     * aop核心实现，主要通过包路径扫描包下AopMethods的方法，获取方法集合
     *
     * 然后通过反射调用该方法
     */
    public class AopCore implements AopInter{
    
        @Override
        public List<Method> getMethods(Class<?> annotationClass, String[] packagePath) {
            Set<Class> classSet = new HashSet<>();
            List<Method> functions = new ArrayList<>();
            for(String path : packagePath){
                String pack = path.replace(".","/");
                try{
                    Enumeration<URL> url = getUrl(pack);
                    if(url==null){
                        return null;
                    }
                    while(url.hasMoreElements()){
                        URL u  = url.nextElement();
                        String pro = u.getProtocol();
                        if("file".equals(pro)){
                            String filePath = URLDecoder.decode(u.getFile(),"UTF-8");
                            findAndAddClassesInPackageByFile(path,filePath,classSet);
                        }
                    }
                }catch (Exception e){
                    e.printStackTrace();
                }
            }
            if(!classSet.isEmpty()){
                for(Class clazz: classSet){
                    Method[] methods = clazz.getMethods();
                    for(Method method : methods){
                        AopMethod aopMethod = method.getAnnotation(AopMethod.class);
                        if(!StringUtils.isEmpty(aopMethod)){
                            functions.add(method);
                        }
                    }
                }
            }
            return functions;
        }
    
        @Override
        public void invoke(Class<? extends AopIntercepter> clazz, Method method,Object args) {
            Method[] interMethods = clazz.getMethods();
            Method before = null;
            Method after = null;
            for(Method m :interMethods){
                if(m.getName().equals("before")){
                    before = m;
                }else if(m.getName().equals("after")){
                    after = m;
                }
            }
    
            try {
                before.invoke(getClass().getClassLoader().loadClass(clazz.getName()).newInstance());
                method.invoke(method.getDeclaringClass().newInstance(),args);
                after.invoke(getClass().getClassLoader().loadClass(clazz.getName()).newInstance());
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            } catch (InstantiationException e) {
                e.printStackTrace();
            }
        }
    
    
    
        private void findAndAddClassesInPackageByFile(String packagePath, String filePath, Set<Class> classSet) {
            File fileDir = new File(filePath);
            if(!fileDir.exists() || !fileDir.isDirectory()){
                return;
            }
            File[] files = fileDir.listFiles(f->f.isDirectory() || f.getName().endsWith(".class"));
    
            for(File file : files){
                if(file.isDirectory()){
                    findAndAddClassesInPackageByFile(packagePath+"."+file.getName(),
                            file.getAbsolutePath(),classSet);
                }else{
                    String className = packagePath+"."+file.getName().substring(0,file.getName().length()-6);
                    try {
                        classSet.add(Thread.currentThread().getContextClassLoader().loadClass(className));
                    } catch (ClassNotFoundException e) {
                        e.printStackTrace();
                        throw new RuntimeException(e.getMessage());
                    }
                }
            }
    
        }
    
    
        private Enumeration<URL> getUrl(String packagePath){
            try {
                Enumeration<URL> enumeration = AopCore.class.getClassLoader().getResources(packagePath);
                if(!enumeration.hasMoreElements()){
                    enumeration = Thread.currentThread().getContextClassLoader().getResources(packagePath);
                    if(!enumeration.hasMoreElements()){
                        return enumeration;
                    }
                }
                return enumeration;
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }
    }

6、然后我们新建AopUser测试接口类，类似于Controller

package com.example.refect.aop.demo;
    
    import com.example.refect.aop.core.AopMethod;
    
    public class AopUser {
    
        @AopMethod("/demo")
        public String getStr(String str){
            System.out.println("AopUser.getStr正在执行,"+str);
            return str;
        }
    
    
        @AopMethod("/user")
        public String getUser(String user){
            System.out.println("AopUser.getUser：正在执行，"+user);
            return user;
        }
    }

7、最后我们定义主方法Base，在主方法中调用AopUser中的接口方法

package com.example.refect.aop;
    
    import com.example.refect.aop.core.AopCore;
    import com.example.refect.aop.core.AopIntercepterImp;
    import com.example.refect.aop.core.AopMethod;
    
    import java.lang.reflect.Method;
    import java.util.List;
    
    /**
     * 本包主要实现自定义拦截aop
     *
     * 简单实现 针对被注解的类中的方法被执行前，执行后调用自定义aop切面方法。
     *
     * 用户可以指定包路径  和  aop注解名称进行aop切面
     */
    public class Base {
    
        public static void main(String[] args) {
            request("/user","张三");
        }
    
        private static void request(String mapping,Object args){
            AopCore core = new AopCore();
            List<Method> methodList = load();
    
            for(Method method :methodList){
                AopMethod annotation = method.getAnnotation(AopMethod.class);
                String value = annotation.value();
                if(value.equals(mapping)){
                    core.invoke(AopIntercepterImp.class,method,args);
                }
            }
        }
    
        private static List<Method> load(){
            String[] paths = new String[]{"com.example.refect.aop.demo"};
            List<Method> methodList = new AopCore().getMethods(AopMethod.class,paths);
            return methodList;
        }
    }

执行主方法，控制台打印：

![70 1][]

断点：

![70 2][]

到此为止，简单的SpringMvc案例算是搭建完毕

[70]: /images/20220512/8a691c72304f4ea9a7567b421faead5c.png
[70 1]: /images/20220512/56221ca5c79f41afb986031a6a7ad57b.png
[70 2]: /images/20220512/68884d58e836412a819295ddefc99008.png