JSON字符串转JavaBean，net.sf.ezmorph.bean.MorphDynaBean cannot be cast to ……

public class Student implements java.io.Serializable{

    /** 
    * @Fields serialVersionUID : TODO
    */ 
    private static final long serialVersionUID = -1943961352036134112L;
    private String sname;
    private Integer age;
    public String getSname() {
        return sname;
    }
    public void setSname(String sname) {
        this.sname = sname;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    
}

JSONObject jobj = JSONObject.fromObject(str);
Student s = (Student) JSONObject.tobean(jobj，Student.class);

import java.util.List;
/**
 * 
* <P>Tiltle: AnalysisModel.java </P>
* <P>Description:模型类  </P>
* @author biyutong
* @date Jun 11, 2012 9:37:54 AM 
* @version:V1.0
 */
public class AnalysisModel implements java.io.Serializable{

    /**
     * 固定条件
     */
    private List<Condition> regularCondtionList;//
    /**
     * 动态条件
     */
    private List<ConditionField> dynamicConFieldList;
    /**
     * 结果
     */
    private List<ResultField> resultField;
    /**
     * 获取前多少条数据
     */
    private Integer topnum;
    /**
     * 顺序还是随机
     */
    private String sortFlag;
    /**
     * 备注
     */
    private String remark;
    /**
     * 模型名称
     */
    private String modelName;
    /**
     * 对应的xml文件名称
     */
    private String fileName;
    public List<Condition> getRegularCondtionList() {
        return regularCondtionList;
    }
    public void setRegularCondtionList(List<Condition> regularCondtionList) {
        this.regularCondtionList = regularCondtionList;
    }
    public List<ConditionField> getDynamicConFieldList() {
        return dynamicConFieldList;
    }
    public void setDynamicConFieldList(List<ConditionField> dynamicConFieldList) {
        this.dynamicConFieldList = dynamicConFieldList;
    }
    public Integer getTopnum() {
        return topnum;
    }
    public void setTopnum(Integer topnum) {
        this.topnum = topnum;
    }
    public String getSortFlag() {
        return sortFlag;
    }
    public void setSortFlag(String sortFlag) {
        this.sortFlag = sortFlag;
    }
    public String getRemark() {
        return remark;
    }
    public void setRemark(String remark) {
        this.remark = remark;
    }

    
    public String getModelName() {
        return modelName;
    }
    public void setModelName(String modelName) {
        this.modelName = modelName;
    }
    public List<ResultField> getResultField() {
        return resultField;
    }
    public void setResultField(List<ResultField> resultField) {
        this.resultField = resultField;
    }
    public String getFileName() {
        return fileName;
    }
    public void setFileName(String fileName) {
        this.fileName = fileName;
    }
    
}

Map<String, Class> classMap = new HashMap<String, Class>();

classMap.put("regularCondtionList", Condition.class);

classMap.put("dynamicConFieldList", ConditionField.class);

classMap.put("resultField", ResultField.class);

AnalysisModel analysisModel=(AnalysisModel) JSONObject.toBean(str, AnalysisModel.class, classMap);