在一个程序中，相对User这个领域对象的诸属性进行修改，用来容纳存储数据的ActionForm是这样写的：

public final class ModifyUserForm extends ActionForm {
    private static final long serialVersionUID = -3447738664240089399L;

    private User user;
    
    public ModifyUserForm(){

    }

    public void reset(ActionMapping mapping, HttpServletRequest request) {
    }

    public ActionErrors validate(ActionMapping mapping,
                                 HttpServletRequest request) {

        ActionErrors errors = new ActionErrors();

        return (errors);

    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }
}

结果，进行页面数据验证的JS能准确无误的进行前段验证，但Action中没有收到请求，验证完毕提交表单后出现下面的异常，

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: javax.servlet.ServletException: BeanUtils.populate
org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:286)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
com.heyang.filter.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:35)

root cause

javax.servlet.ServletException: BeanUtils.populate
org.apache.struts.util.RequestUtils.populate(RequestUtils.java:469)
org.apache.struts.chain.commands.servlet.PopulateActionForm.populate(PopulateActionForm.java:50)
org.apache.struts.chain.commands.AbstractPopulateActionForm.execute(AbstractPopulateActionForm.java:60)
org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:304)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
com.heyang.filter.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:35)

root cause

java.lang.IllegalArgumentException: No bean specified
org.apache.commons.beanutils.PropertyUtilsBean.getPropertyDescriptor(PropertyUtilsBean.java:751)
org.apache.commons.beanutils.BeanUtilsBean.setProperty(BeanUtilsBean.java:937)
org.apache.commons.beanutils.BeanUtilsBean.populate(BeanUtilsBean.java:811)
org.apache.commons.beanutils.BeanUtils.populate(BeanUtils.java:298)
org.apache.struts.util.RequestUtils.populate(RequestUtils.java:467)
org.apache.struts.chain.commands.servlet.PopulateActionForm.populate(PopulateActionForm.java:50)
org.apache.struts.chain.commands.AbstractPopulateActionForm.execute(AbstractPopulateActionForm.java:60)
org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:304)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
com.heyang.filter.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:35)

note The full stack trace of the root cause is available in the Apache Tomcat/6.0.10 logs.

Apache Tomcat/6.0.10

发生这个错误的原因应该是使用工具类commons beanutil向ActionForm中的属性user输入数据时发生了错误，解决这个问题也很简单，在ActionForm内部将属性user实例化即可，代码如下：

public final class ModifyUserForm extends ActionForm {
    private static final long serialVersionUID = -3447738664240089399L;

    private User user=new User();
    
    public ModifyUserForm(){

    }

    public void reset(ActionMapping mapping, HttpServletRequest request) {
    }

    public ActionErrors validate(ActionMapping mapping,
                                 HttpServletRequest request) {

        ActionErrors errors = new ActionErrors();

        return (errors);

    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }
}