在一個程序中，相對User這個領域對象的諸屬性進行修改，用來容納存儲數據的ActionForm是這樣寫的：

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;
    }
}

結果，進行頁面數據驗證的JS能準確無誤的進行前段驗證，但Action中沒有收到請求，驗證完畢提交表單后出現下面的異常，

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

發生這個錯誤的原因應該是使用工具類commons beanutil向ActionForm中的屬性user輸入數據時發生了錯誤，解決這個問題也很簡單，在ActionForm內部將屬性user實例化即可，代碼如下：

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;
    }
}