java.lang.ClassCastException: net.sf.ezmorph.bean.MorphDynaBean cannot be cast to

Java.lang.ClassCastException: net.sf.ezmorph.bean.MorphDynaBean cannot be cast to

在使用JSONObject.toBean的时候，得到的Bean里面的复杂数据类型不能转换成需要的对象类型。

demo:

创建两个实体类Teacher和Student：Teacher中有一个List类型的私有属性

package com.edu.xukai;  

/**
 * @author xukai
 *
 */
public class Student {  

    private String stuNo;  

    private String stuName;  

    public Student() {
    }  

    public Student(String stuNo, String stuName) {
        this.stuNo = stuNo;
        this.stuName = stuName;
    }  

    // getter setter  

    @Override
    public String toString() {
        return "Student [stuNo=" + stuNo + ", stuName=" + stuName + "]";
    }  

}

　　

package com.edu.xukai;  

import java.util.List;  

/**
 * @author xukai
 *
 */
public class Teacher {  

    private String teaId;  

    private String teaName;  

    private List<Student> stus;  

    public Teacher() {
    }  

    public Teacher(String teaId, String teaName, List<Student> stus) {
        this.teaId = teaId;
        this.teaName = teaName;
        this.stus = stus;
    }
//getter setter  

}

　　

测试之前，需要导入相应的jar文件。

需要使用JSONObject,使用的jar文件是json-lib-2.2.3-jdk15.jar

下面是可能缺少jar文件导致的错误和对应的jar：

Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang.exception.NestableRuntimeException
commons-lang-2.4.jar

Caused by: java.lang.ClassNotFoundException: net.sf.ezmorph.Morpher
ezmorph-1.0.6.jar

Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory
commons-logging-1.1.1.jar

Caused by: java.lang.ClassNotFoundException: org.apache.commons.collections.map.ListOrderedMap
commons-collections-3.2.1.jar

Caused by: java.lang.ClassNotFoundException: org.apache.commons.beanutils.DynaBean
commons-beanutils-1.7.0.jar

jar下载链接：点击下载

测试类：

package com.edu.xukai;  

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;  

import net.sf.json.JSONObject;  

/**
 * @author xukai
 *
 */
public class TestJSONObject {  

    public static void main(String[] args) {
        Student student_1 = new Student("学号1", "学生1");
        List<Student> stus = new ArrayList<Student>();
        stus.add(student_1);
        Teacher teacher_1 = new Teacher("编号1", "教师1", stus);
        JSONObject obj = JSONObject.fromObject(teacher_1);
        System.out.println("JSON格式的Teacher->" + obj.toString());
        Teacher teacherBean = (Teacher) JSONObject.toBean(obj, Teacher.class);
        try {
            Student studentBean = teacherBean.getStus().get(0);
            System.out.println(studentBean);
        } catch (Exception e) {
            System.out.println("出现异常");
            e.printStackTrace();
        }
    }  

}

　　运行可以看到控制台打印结果：

JSON格式的Teacher->{"stus":[{"stuName":"学生1","stuNo":"学号1"}],"teaId":"编号1","teaName":"教师1"}
出现异常
java.lang.ClassCastException: net.sf.ezmorph.bean.MorphDynaBean cannot be cast to com.edu.xukai.Student
at com.edu.xukai.TestJSONOb ject.main(TestJSONObject.java:25)

解决办法：使用JSONObject.toBean(jsonObject, beanClass, classMap)

package com.edu.xukai;  

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;  

import net.sf.json.JSONObject;  

/**
 * @author xukai
 *
 */
public class TestJSONObject {  

    public static void main(String[] args) {
        Student student_1 = new Student("学号1", "学生1");
        List<Student> stus = new ArrayList<Student>();
        stus.add(student_1);
        Teacher teacher_1 = new Teacher("编号1", "教师1", stus);
        JSONObject obj = JSONObject.fromObject(teacher_1);
        System.out.println("JSON格式的Teacher->" + obj.toString());  

        // 定义一个Map
        Map<String, Class<Student>> map = new HashMap<String, Class<Student>>();
        map.put("stus", Student.class); // key为teacher私有变量的属性名
        // 使用JSONObject.toBean(jsonObject, beanClass, classMap)
        Teacher teacherBean = (Teacher) JSONObject.toBean(obj, Teacher.class, map);
        try {
            Student studentBean = teacherBean.getStus().get(0);
            System.out.println(studentBean);
        } catch (Exception e) {
            System.out.println("出现异常");
            e.printStackTrace();
        }
    }  

}

控制台打印结果：

JSON格式的Teacher->{"stus":[{"stuName":"学生1","stuNo":"学号1"}],"teaId":"编号1","teaName":"教师1"}
Student [stuNo=学号1, stuName=学生1]