class "org.apache.commons.collections.FastHashMap"'s signer information does not match signer inform

net.sf.json.JSONException: java.lang.SecurityException: class "org.apache.commons.collections.FastHashMap"'s signer information does not match signer information of other classes in the same package
at net.sf.json.JSONObject._fromBean(JSONObject.java:987)
at net.sf.json.JSONObject.fromObject(JSONObject.java:168)
at net.sf.json.JSONObject.fromObject(JSONObject.java:130)
at inc.tech.weixin.test.WeixinTest.main(WeixinTest.java:17)
Caused by: java.lang.SecurityException: class "org.apache.commons.collections.FastHashMap"'s signer information does not match signer information of other classes in the same package
at java.lang.ClassLoader.checkCerts(Unknown Source)
at java.lang.ClassLoader.preDefineClass(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$000(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at org.apache.commons.beanutils.ConvertUtilsBean.<init>(ConvertUtilsBean.java:125)
at org.apache.commons.beanutils.BeanUtilsBean.<init>(BeanUtilsBean.java:110)
at org.apache.commons.beanutils.BeanUtilsBean$1.initialValue(BeanUtilsBean.java:68)
at org.apache.commons.beanutils.ContextClassLoaderLocal.get(ContextClassLoaderLocal.java:91)
at org.apache.commons.beanutils.BeanUtilsBean.getInstance(BeanUtilsBean.java:78)
at org.apache.commons.beanutils.PropertyUtilsBean.getInstance(PropertyUtilsBean.java:101)
at org.apache.commons.beanutils.PropertyUtils.getPropertyDescriptors(PropertyUtils.java:342)
at net.sf.json.JSONObject._fromBean(JSONObject.java:880)
... 3 more

在开发项目时，要用到json-lib-2.3的jar包，及其依赖包。在引入项目后，发现包冲突了。原因是新引入的commons-beautils-1.7.0.jar 与struts1.2版本里的commons-beautils.jar里的org.apache.commons.collections.FastHashMap版本不一致的问题。应该是程序import时，不是引用同一个导致的。

解决办法：

1、将struts里的commons-beautils.jar删除

2、或者 在build path，把需要用的commons-beautifls-1.7.0.jar包的 顺序放到struts包的前面，两者皆可。

至于两种的办法的优劣，暂时还没有体会。