map与java对象相互转换

2024-06-25 18:33| 来源: 网络整理| 查看: 265

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。

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map与java对象相互转换

map与java对象相互转换

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