dubbo的函数返回类，含有有参构造函数时，必须写明一个无参构造函数

最新推荐文章于 2020-12-07 20:16:11 发布

原创最新推荐文章于 2020-12-07 20:16:11 发布 · 2.6k 阅读

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CC 4.0 BY-SA版权

本文介绍了一个关于PageModel类在使用Hessian进行序列化时出现的问题及解决方案。问题表现为在客户端调用时出现HessianProtocolException异常，原因是缺少无参构造函数。通过增加无参构造函数解决了该问题。

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package com.ounersc.ic.adviser.shop.model;

import lombok.Data;

import java.io.Serializable;

@Data
public class PageModel implements Serializable{

    private String begin = "0";
    private String end = "10";
    private Long totalCount = 0L;
    private Long totalPage = 0L;

    public PageModel(Long totalCount,Integer pageIndex,Integer pageSize ){
        this.totalCount = totalCount;
        this.totalPage = (totalCount % pageSize == 0 ? totalCount / pageSize : totalCount / pageSize + 1);

        if (pageIndex < 1){
            pageIndex = 1;
        }

        Integer beginNum = ((pageIndex - 1) * pageSize);
        Integer endNum = ((pageIndex) * pageSize);
        this.begin = beginNum.toString();
        this.end = endNum.toString();
    }

}

PageModel 类在dubbo-Service 工程跑test时正常，但是在客户端调用却抛出异常：

Caused by: com.alibaba.com.caucho.hessian.io.HessianProtocolException: 'com.ounersc.ic.adviser.shop.model.PageModel' could not be instantiated
	at com.alibaba.com.caucho.hessian.io.JavaDeserializer.instantiate(JavaDeserializer.java:275)
	at com.alibaba.com.caucho.hessian.io.JavaDeserializer.readObject(JavaDeserializer.java:155)
	at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObjectInstance(Hessian2Input.java:2067)
	at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObject(Hessian2Input.java:1592)
	at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObject(Hessian2Input.java:1576)
	at com.alibaba.com.caucho.hessian.io.JavaDeserializer$ObjectFieldDeserializer.deserialize(JavaDeserializer.java:396)
	... 27 more
Caused by: java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
	at com.alibaba.com.caucho.hessian.io.JavaDeserializer.instantiate(JavaDeserializer.java:271)
	... 32 more
Caused by: java.lang.NullPointerException
	at com.ounersc.ic.adviser.shop.model.PageModel.<init>(PageModel.java:20)
	... 37 more

原因详见：http://www.bubuko.com/infodetail-1571879.html

解决方法：
加入一个无参数默认构造函数即可

@Data
public class PageModel implements Serializable{

private String begin = "0";
private String end = "10";
private Long totalCount = 0L;
private Long totalPage = 0L;

public PageModel(Long totalCount,Integer pageIndex,Integer pageSize ){
    this.totalCount = totalCount;
    this.totalPage = (totalCount % pageSize == 0 ? totalCount / pageSize : totalCount / pageSize + 1);

    if (pageIndex < 1){
        pageIndex = 1;
    }

    Integer beginNum = ((pageIndex - 1) * pageSize);
    Integer endNum = ((pageIndex) * pageSize);
    this.begin = beginNum.toString();
    this.end = endNum.toString();
}

public PageModel(){

}

}