Java 實現 Map 和 Object 互相轉換的幾種方法

第一種方法是自己加的，後面幾種是摘抄的 :)

參考連結：https://stackoverflow.com/questions/6796187/java-introspection-object-to-map

/**
 * 使用 com.fasterxml.jackson.databind.ObjectMapper 進行轉換
 */
class A {

    public static Object mapToObject (Map<String, Object> map, Class<?> beanClass) throws Exception {
        if (map == null) {
            return null;
        }

        ObjectMapper objectMapper = new ObjectMapper();
        Object obj = objectMapper.convertValue(map, beanClass);  

        return obj;
    }

    public static Map<?, ?> objectToMap (Object obj) {
        if (obj == null) {
            return null;
        }

        ObjectMapper objectMapper = new ObjectMapper();
        Map<?, ?> mappedObject = objectMapper.convertValue(obj, Map.class);

        return mappedObject;
    }
}

/** 
 * 使用 org.apache.commons.beanutils 進行轉換 
 */ 
class B {  

    public static Object mapToObject(Map<String, Object> map, Class<?> beanClass) throws Exception {    
        if (map == null) {
            return null;
        }

        Object obj = beanClass.newInstance();  

        org.apache.commons.beanutils.BeanUtils.populate(obj, map);  

        return obj;  
    }    

    public static Map<?, ?> objectToMap(Object obj) {  
        if (obj == null) {
            return null;
        }

        return new org.apache.commons.beanutils.BeanMap(obj);  
    }    

}  

/** 
 * 使用 Introspector 進行轉換 
 */ 
class C {  

    public static Object mapToObject(Map<String, Object> map, Class<?> beanClass) throws Exception {    
        if (map == null) {
            return null;
        }

        Object obj = beanClass.newInstance();  

        BeanInfo beanInfo = Introspector.getBeanInfo(obj.getClass());    
        PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();    
        for (PropertyDescriptor property : propertyDescriptors) {  
            Method setter = property.getWriteMethod();    
            if (setter != null) {  
                setter.invoke(obj, map.get(property.getName()));   
            }  
        }  

        return obj;  
    }    

    public static Map<String, Object> objectToMap(Object obj) throws Exception {    
        if (obj == null) {
            return null;
        }    

        Map<String, Object> map = new HashMap<String, Object>();   

        BeanInfo beanInfo = Introspector.getBeanInfo(obj.getClass());    
        PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();    
        for (PropertyDescriptor property : propertyDescriptors) {    
            String key = property.getName();    
            if (key.compareToIgnoreCase("class") == 0) {   
                continue;  
            }  
            Method getter = property.getReadMethod();  
            Object value = getter!=null ? getter.invoke(obj) : null;
            map.put(key, value);  
        }    

        return map;  
    }    

}  

/** 
 * 使用 reflect 進行轉換 
 */ 
class D {  

    public static Object mapToObject(Map<String, Object> map, Class<?> beanClass) throws Exception {    
        if (map == null) {
            return null;
        }

        Object obj = beanClass.newInstance();  

        Field[] fields = obj.getClass().getDeclaredFields();   
        for (Field field : fields) {    
            int mod = field.getModifiers();    
            if (Modifier.isStatic(mod) || Modifier.isFinal(mod)) {    
                continue;    
            }    

            field.setAccessible(true);    
            field.set(obj, map.get(field.getName()));   
        }   

        return obj;    
    }    

    public static Map<String, Object> objectToMap(Object obj) throws Exception {    
        if (obj == null) {    
            return null;    
        }   

        Map<String, Object> map = new HashMap<String, Object>();    

        Field[] declaredFields = obj.getClass().getDeclaredFields();    
        for (Field field : declaredFields) {    
            field.setAccessible(true);  
            map.put(field.getName(), field.get(obj));  
        }    

        return map;  
    }   
}