map与java对象相互转换

最近，研究map与java对象之间的相互转换，总结了5种方法：

第一种：使用org.apache.commons.beanutils转换

用到的主要jar包：commons-beanutils-1.9.3.jar

//map转java对象
public static Object mapToObject(Map map, Class beanClass)
			throws Exception {
		if (map == null) {
			return null;
		}
		Object obj = beanClass.newInstance();
		BeanUtils.populate(obj, map);
		return obj;
	}

//java对象转map
public static Map objectToMap(Object obj) {
		if (obj == null)
			return null;
		return new BeanMap(obj);
	}

在使用该方法进行java对象转map时，可能会发生以下错误：

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/collections/Transformer
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
	at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
	at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
	at org.apache.commons.beanutils.BeanMap.createTypeTransformers(BeanMap.java:132)
	at org.apache.commons.beanutils.BeanMap.(BeanMap.java:68)
	at com.example2.pojo.PojoToMap.objectToMap(PojoToMap.java:23)
	at com.example2.pojo.PojoToMap.main(PojoToMap.java:16)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.collections.Transformer
	at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
	at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
	... 16 more

解决方法见本人的另一篇文章： https://blog.csdn.net/liuyunyihao/article/details/86596595

第二种：使用Introspector转换

//map转java对象
public static Object mapToObject(Map 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;
    }

//java对象转map
public static Map objectToMap(Object obj) throws Exception {
	if (obj == null) {
		return null;
	}
	Map map = new HashMap();
	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;
}

第三种：使用reflect转换

//map转java对象
public static Object mapToObject(Map map, Class beanClass) throws Exception {
        if (map == null) {
            return null;
        }
        Object object = beanClass.newInstance();
        Field[] fields = beanClass.getDeclaredFields();
        for (Field field : fields) {
            int mod = field.getModifiers();
            if (Modifier.isFinal(mod) || Modifier.isStatic(mod)) {
                continue;
            }
            field.setAccessible(true);
            field.set(object, map.get(field.getName()));
        }
        return object;
    }

//java对象转map
public static Map objectToMap(Object obj) throws Exception {
	if (obj == null) {
		return null;
	}
	Map map = new HashMap();
	Field[] declaredFields = obj.getClass().getDeclaredFields();
	for (Field field : declaredFields) {
		field.setAccessible(true);
		map.put(field.getName(), field.get(obj));
	}
	return map;
}

第四种：使用net.sf.cglib.beans.BeanMap转换

用到的主要jar包：cglib-2.2.2.jar

//map转java对象
public static Object mapToObject(Map map, Class beanClass) throws Exception {
    Object object = beanClass.newInstance();
    BeanMap beanMap = BeanMap.create(object);
    beanMap.putAll(map);
    return object;
}

//java对象转map
public static Map objectToMap(Object obj) {
    Map map = Maps.newHashMap();
    if (obj != null) {
        BeanMap beanMap = BeanMap.create(obj);
        for (Object key : beanMap.keySet()) {
            map.put(key + "", beanMap.get(key));
        }
    }
    return map;
}

在使用本方法进行map转java对象时，可能会发生以下错误：

Exception in thread "main" java.lang.NoClassDefFoundError: org/objectweb/asm/Type
	at net.sf.cglib.core.TypeUtils.parseType(TypeUtils.java:184)
	at net.sf.cglib.core.KeyFactory.(KeyFactory.java:66)
	at net.sf.cglib.beans.BeanMap$Generator.(BeanMap.java:64)
	at net.sf.cglib.beans.BeanMap.create(BeanMap.java:56)
	at com.example2.pojo.MapToPojo.mapToBean(MapToPojo.java:27)
	at com.example2.pojo.MapToPojo.main(MapToPojo.java:18)
Caused by: java.lang.ClassNotFoundException: org.objectweb.asm.Type
	at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
	at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
	... 6 more

解决方法见本人的另一篇文章：https://blog.csdn.net/liuyunyihao/article/details/86593722

第五种：使用json转换

用到的主要jar包：fastjson-1.2.54.jar

//map转java对象
public static Object mapToObject(Map map, Class beanClass) throws Exception {
    String jsonStr = JSONObject.toJSONString(map);
    return JSONObject.parseObject(jsonStr, beanClass);
}

//java对象转map
public static Map objectToMap(Object obj) {
    String jsonStr = JSONObject.toJSONString(obj);
    return JSONObject.parseObject(jsonStr);
}

以上方法本人均实际测试通过。