使用java反射，自定義springMvc簡單案例
阿新 • • 發佈：2018-11-13
目前javaWeb開發領域，SpringMvc已經是絕大部分中小公司必選框架，那麼springMvc是如何實現的呢。這裡通過一個簡單的小案例來演示一下。
首先看一下案例的結構圖
目前springBoot專案比較流行，這裡新建一個springBoot專案，先引入專案依賴
<?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/> <!-- lookup parent from repository --> </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註解，這個註解可以理解為RequestMapping
package com.example.refect.aop.core;
import java.lang.annotation.*;
/**
* 方法註解，這裡類似RequestMapping
*/
@Documented
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface AopMethod {
String value() default "";
}
2、新建攔截器介面AopIntercepter，這裡可以理解為SpringMvc攔截器
package com.example.refect.aop.core;
/**
* 攔截器
*/
public abstract class AopIntercepter {
abstract void before();
abstract void after();
}
3、新建攔截器實現類AopIntercepterImp
package com.example.refect.aop.core; /** * 攔截器實現 */ public class AopIntercepterImp extends AopIntercepter { @Override public void before() { System.out.println("呼叫前執行：before"); } @Override public void after() { System.out.println("呼叫後執行：after"); } }
4、新建aop核心介面 AopInter
package com.example.refect.aop.core;
import java.lang.reflect.Method;
import java.util.List;
/**
* aop核心介面
*/
public interface AopInter {
List<Method> getMethods(Class<?> annotation, String[] packagePath);
void invoke(Class<? extends AopIntercepter> clazz, Method method,Object args);
}5、新建核心介面實現類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核心實現，主要通過包路徑掃描包下AopMethods的方法，獲取方法集合
*
* 然後通過反射呼叫該方法
*/
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、然後我們新建AopUser測試介面類，類似於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正在執行,"+str);
return str;
}
@AopMethod("/user")
public String getUser(String user){
System.out.println("AopUser.getUser：正在執行，"+user);
return user;
}
}
7、最後我們定義主方法Base，在主方法中呼叫AopUser中的介面方法
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;
/**
* 本包主要實現自定義攔截aop
*
* 簡單實現 針對被註解的類中的方法被執行前，執行後呼叫自定義aop切面方法。
*
* 使用者可以指定包路徑 和 aop註解名稱進行aop切面
*/
public class Base {
public static void main(String[] args) {
request("/user","張三");
}
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;
}
}
執行主方法，控制檯列印：
斷點：
到此為止，簡單的SpringMvc案例算是搭建完畢