JSONUtil.bean2Json()报Property 'key' of class has no read method. SKIPPED的问题处理

错误警告信息描述：

net.sf.json.JSONObject.defaultBeanProcessing(JSONObject.java:769) 
Property ‘handler‘ of class com.vrv.cems.mgr.domain.Manager_$$_javassist_182 has no read method. SKIPPED

问题分析：

JsonUtil.bean2Json(queryHistogramVO,new String[]{}));将VO对象转换成JSON对象格式jsonUtil包路径：queryHistogramVO 对象的属性和方法：public class HistogramVO { ???private Integer userNum; ???private Integer topCategory; ???private Integer lastUserNum; ???public Integer getCurrentUser() { ???????return this.userNum; ???} ???public Integer getTopCategory() { ???????return topCategory; ???} ???public void setTopCategory(Integer topCategory) { ???????this.topCategory = topCategory; ???} ???public void setUserNum(Integer userNum) { ???????this.userNum = userNum; ???} ???public Integer getLastUserNum() { ???????return lastUserNum; ???} ???public void setLastUserNum(Integer lastUserNum) { ???????this.lastUserNum = lastUserNum; ???} ??}

　　肉眼看上去这个类没有任何问题，仔细观察发现 属性"userNum"的get方法为"getCurrentUser()"

详细分析：

1、jsonutil调用类图分析：

　　JsonUtil工具类是通过JSONObject.fromObject()方法转换的，查看源码，对fromObject详细分析发现代码：

　　　　　　//这一句话很关键下面详细讲解 ?????????PropertyDescriptor[] pds = PropertyUtils.getPropertyDescriptors( bean ); ????????PropertyFilter jsonPropertyFilter = jsonConfig.getJsonPropertyFilter(); ????????Class beanClass = bean.getClass(); ????????for( int i = 0; i < pds.length; i++ ){ ???????????String key = pds[i].getName(); ???????????if( exclusions.contains( key ) ){ ??????????????continue; ???????????} ???????????if( jsonConfig.isIgnoreTransientFields() && isTransientField( key, beanClass ) ){ ??????????????continue; ???????????} ???????????Class type = pds[i].getPropertyType(); ???????????//判断如果类的get方法存在则设置属性值 ???????????if( pds[i].getReadMethod() != null ){ ?????????????//--------------中间的代码省略掉 ??????????????setValue( jsonObject, key, value, type, jsonConfig ); ???????????}else{ ??????????????//当get方法不存在报警告错误 ??????????????String warning = "Property ‘" + key + "‘ has no read method. SKIPPED"; ??????????????fireWarnEvent( warning, jsonConfig ); ??????????????log.warn( warning ); ???????????} ????????}

　　PropertyDescriptor[] pds = PropertyUtils.getPropertyDescriptors( bean );

　　这段代码是获取Bean所有的属性信息并将他封装成 PropertyDescriptor描述类。

　　深入 getPropertyDescriptors()分析：

　　　　　if (beanClass == null) { ???????????throw new IllegalArgumentException("No bean class specified"); ???????} ???????// Look up any cached descriptors for this bean class ???????PropertyDescriptor[] descriptors = null; ???????descriptors = ???????????????(PropertyDescriptor[]) descriptorsCache.get(beanClass); ???????if (descriptors != null) { ???????????return (descriptors); ???????} ???????// Introspect the bean and cache the generated descriptors ???????BeanInfo beanInfo = null; ???????try { ???????????beanInfo = Introspector.getBeanInfo(beanClass); ???????} catch (IntrospectionException e) { ???????????return (new PropertyDescriptor[0]); ???????} ???????descriptors = beanInfo.getPropertyDescriptors(); ???????if (descriptors == null) { ???????????descriptors = new PropertyDescriptor[0]; ???????}

　　上面是关键部分，他是通过java内省机制获取Bean的属性方法，并返回BeanInfo类。

　　获取属性的规则：

　　通过上面的分析，HistogramVO类有setUserNum()方法确没有对应的getUserNum()方法导致报""json.JSONObject - Property ‘userNum‘ has no read method. SKIPPED"警告错误。

　　添加getUserNum()方法即解决问题。