webee自己实现一个简单的mvc架构

小咪咪 2022-02-23 10:48 323阅读 0赞

### 1、整体的目录： ###

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首先定义一个类扫描器：

#### 2、ClassScanner ####

package cn.com.hsl.webEE.utils;
    
    import java.io.File;
    import java.io.IOException;
    import java.net.JarURLConnection;
    import java.net.URL;
    import java.util.Enumeration;
    import java.util.HashMap;
    import java.util.Map;
    import java.util.jar.JarEntry;
    import java.util.jar.JarFile;
    
    public class ClassScanner { 
    
    	public static Map<String, Class<?>> scan(String pkg) { 
    		Map<String, Class<?>> result = new HashMap<String, Class<?>>();
    		String basePath = pkg;
    		if (pkg.contains(".")) { 
    			basePath = pkg.replace(".", "/");
    		}
    		
    		Enumeration<URL> urls;
    		try { 
    			urls = Thread.currentThread().getContextClassLoader().getResources(basePath);
    			while (urls.hasMoreElements()) { 
    				URL url = (URL) urls.nextElement();
    				//如果是本地的文件
    				if ("file".equals(url.getProtocol())) { 
    					File folder = new File(url.getPath());
    					scanFolder(pkg, folder, result);
    					
    				//如果是Jar包的文件
    				} else if ("jar".equals(url.getProtocol())) { 
    					scanjar(url, basePath, result);
    				}
    			}
    		} catch (IOException e) { 
    			e.printStackTrace();
    		}
    		return result;
    	}
    	
    	private static void scanFolder(String root, File folder, Map<String, Class<?>> result) { 
    		for (File file : folder.listFiles()) { 
    			String name = file.getName();
    			if (file.isDirectory()) { 
    				scanFolder(root + "." + name, file, result);
    			} else { 
    				try { 
    					//只扫描以 .class 结尾的文件
    					if (!name.endsWith(".class")) { 
    						continue;
    					}
    					String className = name.substring(0, name.lastIndexOf("."));
    					
    					//不掃描內部類
    					if (className.matches("[\\w+$*\\w*/]+\\$\\d+$")) { 
    						continue;
    					}
    					String classPath = root + "." + className;
    					result.put(className, Class.forName(classPath));
    				} catch (ClassNotFoundException e) { 
    					e.printStackTrace();
    				}
    			}
    		}
    	}
    	
    	private static void scanjar(URL url, String basePath, Map<String, Class<?>> result) throws IOException { 
    		JarURLConnection connection = (JarURLConnection) url.openConnection();
    		if (connection != null) { 
    			JarFile jarFile = connection.getJarFile();
    			if (jarFile != null) { 
    			
    				//Jar包获取的将是这个jar包中的全部文件
    				Enumeration<JarEntry> entryEnu = jarFile.entries();
    				while (entryEnu.hasMoreElements()) { 
    					JarEntry jarEntry = (JarEntry) entryEnu.nextElement();
    					String entryClass = jarEntry.getName();
    					if (entryClass == null || !entryClass.endsWith(".class")){ 
    						continue;
    					}
    					
    					String entryName = entryClass.substring(0, entryClass.lastIndexOf("."));
    					if (entryName.matches("[\\w+$*\\w*/]+\\$\\d+$")) { 
    						continue;
    					}
    					
    					//需要过滤其他包目录下的文件
    					if (entryName.startsWith(basePath)) { 
    						try { 
    							result.put(entryName, Class.forName(entryName.replace("/", ".")));
    						} catch (ClassNotFoundException e) { 
    							e.printStackTrace();
    						}
    					}
    				}
    			}
    		}
    	}
    	
    	public static void main(String[] args) { 
    		Map<String, Class<?>> classMap = ClassScanner.scan("cn");
    		System.out.println(classMap);
    	}
    	
    }

其次定义一些注解：

#### 3.1、Autowired ####

package cn.com.hsl.webEE.annotation;
    
    import static java.lang.annotation.ElementType.FIELD;
    import static java.lang.annotation.ElementType.TYPE;
    import static java.lang.annotation.RetentionPolicy.RUNTIME;
    
    import java.lang.annotation.Retention;
    import java.lang.annotation.Target;
    
    @Retention(RUNTIME)
    @Target({  TYPE, FIELD })
    public @interface Autowired { 
    	//注入的Bean实例
    	String value();
    }

#### 3.2、Bean ####

package cn.com.hsl.webEE.annotation;
    
    import static java.lang.annotation.ElementType.TYPE;
    import static java.lang.annotation.RetentionPolicy.RUNTIME;
    
    import java.lang.annotation.Retention;
    import java.lang.annotation.Target;
    
    @Retention(RUNTIME)
    @Target(TYPE)
    public @interface Bean { 
    	//Bean在容器中的名称
    	String value();
    	//是否是单例
    	boolean single() default true;
    }

定义一些实体类，这些实体类用来保存 在多例的时候 类和属性的相关信息：

#### 4.1、BeanEntity ####

package cn.com.hsl.webEE.entity;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class BeanEntity { 
    
    	private String beanName;
    	private String className;
    	private Class<?> clazz;
    	private List<FieldEntity> fields = new ArrayList<FieldEntity>();
    	
    	public String getBeanName() { 
    		return beanName;
    	}
    	public void setBeanName(String beanName) { 
    		this.beanName = beanName;
    	}
    	public String getClassName() { 
    		return className;
    	}
    	public void setClassName(String className) { 
    		this.className = className;
    	}
    	public Class<?> getClazz() { 
    		return clazz;
    	}
    	public void setClazz(Class<?> clazz) { 
    		this.clazz = clazz;
    	}
    	public List<FieldEntity> getFields() { 
    		return fields;
    	}
    	public void setFields(List<FieldEntity> fields) { 
    		this.fields = fields;
    	}
    }

#### 4.2、FieldEntity ####

package cn.com.hsl.webEE.entity;
    
    import java.lang.reflect.Field;
    
    public class FieldEntity { 
    
    	private Field field;
    	private String beanName;
    	
    	public Field getField() { 
    		return field;
    	}
    	public void setField(Field field) { 
    		this.field = field;
    	}
    	public String getBeanName() { 
    		return beanName;
    	}
    	public void setBeanName(String beanName) { 
    		this.beanName = beanName;
    	}
    	
    	
    }

封装Bean工厂：

#### 4、ApplicationContext ####

package cn.com.hsl.webEE.core;
    
    import java.lang.reflect.Field;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    import java.util.Map.Entry;
    
    import cn.com.hsl.webEE.annotation.Autowired;
    import cn.com.hsl.webEE.annotation.Bean;
    import cn.com.hsl.webEE.entity.BeanEntity;
    import cn.com.hsl.webEE.entity.FieldEntity;
    import cn.com.hsl.webEE.utils.ClassScanner;
    
    public class ApplicationContext { 
    
    	private Map<String, Class<?>> classMap;
    	
    	//单例Bean容器
    	private Map<String, Object> beans = new HashMap<String, Object>();
    	
    	//多例Bean容器
    	private Map<String, BeanEntity> entities = new HashMap<String, BeanEntity>();
    	
    	public ApplicationContext(String pkg) { 
    		init(pkg);
    	}
    	
    	private void init(String pkg) { 
    		this.classMap = ClassScanner.scan(pkg);
    		for (Entry<String, Class<?>> entry : classMap.entrySet()) { 
    			//String beanName = entry.getKey();
    			Class<?> beanClass = entry.getValue();
    			if (beanClass.isAnnotationPresent(Bean.class)) { 
    				initBean(beanClass);
    			}
    		}
    	}
    	
    	private Object initBean(Class<?> clazz) { 
    		Object obj = null;
    		try { 
    			Bean bean = clazz.getAnnotation(Bean.class);
    			String beanName = bean.value();
    			
    			//如果是单例
    			if(bean.single()) { 
    				if (beans.containsKey(beanName)) { 
    					return beans.get(beanName);
    				}
    				
    				obj = initSigleBean(clazz);
    				beans.put(beanName, obj);
    				
    			//如果是多例，只是保存BeanEntity
    			} else { 
    				initMultBean(beanName, clazz);
    			}
    		} catch (Exception e) { 
    			e.printStackTrace();
    		}
    		
    		return obj;
    	}
    	
    	private Object initSigleBean(Class<?> clazz) throws Exception { 
    		Object obj = clazz.newInstance();
    		Field[] fields = clazz.getDeclaredFields();
    		for (Field field : fields) { 
    			if (field.isAnnotationPresent(Autowired.class)) { 
    				Autowired autowired = field.getAnnotation(Autowired.class);
    				String fieldBeanName = autowired.value();
    				
    				//从容器中去拿，如果有直接使用，如果没有，先去创建，再使用
    				Object o = getBean(fieldBeanName);
    				if (o == null) { 
    					
    					//如果这个field是多例的，则没有返回具体的实例，而是一个beanEntity
    					o = initBean(field.getType());
    					
    					//这时需要再次获取一次，实例化一下。
    					if (o == null) { 
    						o = getBean(fieldBeanName);
    					}
    				}
    				
    				field.setAccessible(true);
    				field.set(obj, o);
    			}
    		}
    		
    		return obj;
    	}
    	
    	private void initMultBean(String beanName, Class<?> clazz) { 
    		Field[] fields = clazz.getDeclaredFields();
    		BeanEntity beanEntity = new BeanEntity();
    		beanEntity.setBeanName(beanName);
    		beanEntity.setClazz(clazz);
    		for (Field field : fields) { 
    			if (field.isAnnotationPresent(Autowired.class)) { 
    				Autowired autowired = field.getAnnotation(Autowired.class);
    				FieldEntity fieldEntity = new FieldEntity();
    				fieldEntity.setBeanName(autowired.value());
    				fieldEntity.setField(field);
    				beanEntity.getFields().add(fieldEntity);
    			}
    		}
    		entities.put(beanName, beanEntity);
    	}
    	
    	public Object getBean(String beanName) throws Exception { 
    		Object obj = null;
    		obj = beans.get(beanName);
    		if (obj == null) { 
    			if (entities.containsKey(beanName)) { 
    				BeanEntity beanEntity = entities.get(beanName);
    				Class<?> clazz = beanEntity.getClazz();
    				if (clazz != null) { 
    					obj = clazz.newInstance();
    					List<FieldEntity> fieldEntities = beanEntity.getFields();
    					for (FieldEntity fieldEntity : fieldEntities) { 
    						Field field = fieldEntity.getField();
    						field.setAccessible(true);
    						field.set(obj, getBean(fieldEntity.getBeanName()));
    					}
    				}
    			}
    		}
    		return obj;
    	}
    }

测试：

#### 5.1、UserDao ####

package cn.com.hsl.webEE;
    
    import cn.com.hsl.webEE.annotation.Bean;
    
    @Bean("userDao")
    public class UserDao { 
    
    	public void addUser() { 
    		System.out.println(this.getClass().getName() + ".addUser().");
    	}
    	
    }

#### 5.2、UserService ####

package cn.com.hsl.webEE;
    
    import cn.com.hsl.webEE.annotation.Autowired;
    import cn.com.hsl.webEE.annotation.Bean;
    
    @Bean("userservice")
    public class UserService { 
    
    	@Autowired("userDao")
    	private UserDao userDao;
    
    	public void add() { 
    		userDao.addUser();
    	}
    }

#### 5.3、App ####

package cn.com.hsl.webEE;
    
    import cn.com.hsl.webEE.core.ApplicationContext;
    
    /** * Hello world! * */
    public class App { 
    	public static void main(String[] args) { 
    		try { 
    			ApplicationContext context = new ApplicationContext("cn.com.hsl");
    			UserService userService = (UserService) context.getBean("userservice");
    			userService.add();
    		} catch (Exception e) { 
    			e.printStackTrace();
    		}
    	}
    }

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