自定义Java web框架(二)
接续上一章自定义Java web框架(一)
的内容,这章主要是讲解如何实现类加载器,实现个Bean容器,用于生产Bean实例。
先看文件目录如下:
做开发思路是很重要的。首先,我们的目的是要获取Bean的实例,这样就需要一个Bean的容器,通过这个容器动态的获取Bean实例,如何实现这个Bean的容器呢?Java中使用反射的方式得到Bean实例放置到Map容器中。如何得到Bean实例呢?参考Spring框架中的Controller层、Service层等都是Bean实例,因此这里定义了几个Controller、Service的注解,作为Bean实例。同时为了动态获取Bean实例,自己实现一个类加载器。这样,思路已经很清晰了吧。
为了易于阅读,下面画个主要的类关系,其中每个类的主要方法写出来。
先开发一个类加载器,代码如下:
public class ClassUtil {
private static final Logger LOGGER = LoggerFactory.getLogger(ClassUtil.class);
private static final char DOT_CHAR = '.';
private static final char SLASH_CHAR = '/';
/**
* 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;
}
/**
* 获取指定包下的所有类
* @param packageName
* @return
*/
public static Set<Class<?>> getClassSet(String packageName) {
Set<Class<?>> classSet = new HashSet<>();
try {
Enumeration<URL> urls = getClassLoader().getResources(packageName.replace(DOT_CHAR, SLASH_CHAR));
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);
}
}
}
} catch (Exception e) {
LOGGER.error("get class set failure", e);
throw new RuntimeException(e);
}
return classSet;
}
/**
* 添加类
* @param classSet
* @param packagePath
* @param packageName
*/
private static void addClass(Set<Class<?>> classSet, String packagePath, String packageName) {
File[] files = new File(packagePath).listFiles(new FileFilter() {
@Override
public boolean accept(File file) {
return (file.isFile() && file.getName().endsWith(".class")) || file.isDirectory();
}
});
for (File file : files) {
String fileName = file.getName();
if (file.isFile()) {
String className = fileName.substring(0, fileName.lastIndexOf("."));
if (StringUtils.isNotEmpty(packageName)) {
className = packageName + "." + className;
}
doAddClass(classSet, className);
} else {
String subPackagePath = fileName;
if (StringUtils.isNotEmpty(packagePath)) {
subPackagePath = packagePath + "/" + subPackagePath;
}
String subPackageName = fileName;
if (StringUtils.isNotEmpty(packageName)) {
subPackageName = packageName + "/" + subPackageName;
}
addClass(classSet, subPackagePath, subPackageName);
}
}
}
/**
* 类放置到set
* @param classSet
* @param className
*/
private static void doAddClass(Set<Class<?>> classSet, String className) {
Class<?> cls = loadClass(className, false);
classSet.add(cls);
}
}
然后定义几个常用注解
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Action {
String value();
}
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Controller {
}
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Inject {
}
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Service {
}
定义一个帮助类
public final class ClassHelper {
/**
* 定义类集合(用于存放所加载的类)
*/
private static final Set<Class<?>> CLASS_SET;
static {
String basePackage = ConfigHelper.getAppBasePackage() ;
CLASS_SET = ClassUtil.getClassSet(basePackage);
}
/**
* 获取应用包名下的所有类
* @return
*/
public static Set<Class<?>> getClassSet() {
return CLASS_SET;
}
/**
* 获取应用包下的所有service类
* @return
*/
public static Set<Class<?>> getServiceClassSet() {
Set<Class<?>> classSet = new HashSet<>();
for (Class<?> cls: CLASS_SET) {
if (cls.isAnnotationPresent((Service.class))) {
classSet.add(cls);
}
}
return classSet;
}
/**
* 获取应用包名下的所有controller类
* @return
*/
public static Set<Class<?>> getControllerClassSet() {
Set<Class<?>> classSet = new HashSet<>();
for (Class<?> cls : CLASS_SET) {
if (cls.isAnnotationPresent(Controller.class)) {
classSet.add(cls);
}
}
return classSet;
}
/**
* 获取应用包下所有的bean类(包括:Service。Controller 等)
* @return
*/
public static Set<Class<?>> getBeanClassSet() {
Set<Class<?>> beanClassSet = new HashSet<>();
beanClassSet.addAll(getControllerClassSet());
beanClassSet.addAll(getServiceClassSet());
return beanClassSet;
}
使用反射获取Bean实例
public final class ReflectionUtil {
private static final Logger LOGGER = LoggerFactory.getLogger(ReflectionUtil.class);
/**
* 创建实例
*/
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;
}
/**
* 调用方法
*/
public static Object invokeMethod(Object obj, Method method, Object...args) {
Object result;
try {
method.setAccessible(true);
result = method.invoke(obj, args);
} catch (Exception e) {
LOGGER.error("invoke method failure", e);
throw new RuntimeException(e);
}
return result;
}
/**
* 设置成员变量的值
*/
public static void setField(Object obj, Field field, Object value) {
try {
field.setAccessible(true);
field.set(obj, value);
} catch(Exception e) {
LOGGER.error("set field failure", e);
throw new RuntimeException(e);
}
}
}```
定义Bean的帮助类
public 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>();
static {
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);
}
}
``
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