报错信息为: 
Caused by: java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.commons.beanutils.PropertyUtilsBean.invokeMethod(PropertyUtilsBean.java:2155)
	at org.apache.commons.beanutils.PropertyUtilsBean.getSimpleProperty(PropertyUtilsBean.java:1323)
	at org.apache.commons.beanutils.PropertyUtilsBean.getNestedProperty(PropertyUtilsBean.java:762)
	at org.apache.commons.beanutils.PropertyUtilsBean.getProperty(PropertyUtilsBean.java:837)
	at org.apache.commons.beanutils.PropertyUtils.getProperty(PropertyUtils.java:426)
	at net.sf.json.JSONObject.defaultBeanProcessing(JSONObject.java:749)
	... 55 more
Caused by: java.lang.IllegalArgumentException
	at java.sql.Date.getHours(Date.java:187)
	... 65 more
  
原因: 
java.sql.util.Date类的getHours方法已经被弃用,但是net.sf.json.JSONObject.fromObject(javaObject)进行json序列化的时候仍然调用了这个方法。  
这篇博客中描述的很详细:https://segmentfault.com/a/1190000016937108  
结局方法: 
json-lib有一个配置类JsonConfig,通过JsonConfig可以注册一个字段处理器,通过实现JsonValueProcessor接口,将Date格式化后使用。  
加入依赖:  
		<dependency>
            <groupId>net.sf.json-lib</groupId>
            <artifactId>json-lib</artifactId>
            <version>2.4</version>
            <classifier>jdk15</classifier>
        </dependency>
  
实现接口:  
@Test
public void testJson(){
    Map<String, Object> mp = new ModelMap();
    mp.put("server",server.getAll());
    JsonConfig config = new JsonConfig();
    config.registerJsonValueProcessor(java.sql.Date.class, new JsonValueProcessor() {
        private SimpleDateFormat sd = new SimpleDateFormat("yyyy-MM-dd");
        @Override
        public Object processArrayValue(Object arg0, JsonConfig arg1) {
            return null;
        }
        @Override
        public Object processObjectValue(String arg0, Object arg1, JsonConfig arg2) {
            return arg1 == null ? "" : sd.format(arg1);
        }
    });
    JSONObject jsonObject = JSONObject.fromObject(mp);
    String msg = jsonObject.toString();
    System.out.println(msg);
}
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