Spring+Vue+ElementUI的前后端分离开发项目中，前端向后端发送请求，后端返回错误：Cannot deserialize instance of `java.util.LinkedHashMap` out of START_ARRAY token

问题描述：

　　Spring+Vue+ElementUI的前后端分离开发项目中，前端向后端发送请求，后端返回错误：Cannot deserialize instance of `java.util.LinkedHashMap` out of START_ARRAY token。

前端代码：

        // 获取分页数据
        findPage: function (data) {
            if(data !== null) {
                this.pageRequest = data.pageRequest
            }
            this.pageRequest.params = [{name:'name', value:this.filters.name}];
　　　　　　　this.$api.user.findPage(this.pageRequest).then((res) => {
                this.pageResult = res.data
                this.findUserRoles()
            }).then(data!=null?data.callback:'')
        }

后端代码：

分页请求参数Java类：

package com.XXXXX.XXXXX.core.page;//包名

import java.util.HashMap;
import java.util.Map;

/**
 * 分页请求*/
public class PageRequest {
    //当前页码
    private int pageNum = 1;
    //每页数量
    private int pageSize = 10;
    //其它查询参数
    private Map<String, Object> params = new HashMap<>();
    
    public int getPageNum() {
        return pageNum;
    }
    public void setPageNum(int pageNum) {
        this.pageNum = pageNum;
    }
    public int getPageSize() {
        return pageSize;
    }
    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }
    public Map<String, Object> getParams() {
        return params;
    }
    public void setParams(Map<String, Object> params) {
        this.params = params;
    }
    public Object getParam(String key) {
        return getParams().get(key);
    }   
}

后端请求控制器类：

package com.XXXXX.XXXXX.admin.controller;//包名

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.access.prepost.PreAuthorize;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.XXXXX.XXXXX.admin.model.SysLoginLog;//导入的包名
import com.XXXXX.XXXXX.admin.service.SysLoginLogService;
import com.XXXXX.XXXXX.core.http.HttpResult;
import com.XXXXX.XXXXX.core.page.PageRequest;

//登录日志控制器
@RestController
@RequestMapping("loginlog")
public class SysLoginLogController {

    @Autowired
    private SysLoginLogService sysLoginLogService;

    @PreAuthorize("hasAuthority('sys:loginlog:view')")
    @PostMapping(value="/findPage")
    public HttpResult findPage(@RequestBody PageRequest pageRequest) {
        return HttpResult.ok(sysLoginLogService.findPage(pageRequest));
    }
    
    @PreAuthorize("hasAuthority('sys:loginlog:delete')")
    @PostMapping(value="/delete")
    public HttpResult delete(@RequestBody List<SysLoginLog> records) {
        return HttpResult.ok(sysLoginLogService.delete(records));
    }
}

解决办法：

　　经过分析发现，后端java类PageRequest的代码中已经声明params为Map<String, Object>类型，但是前端传入的JSON字符串却是数组类型的，后台无法完成转化，因此将前端的数组删除，改为对象类型。否则，辉抛出Cannot deserialize instance of `java.util.LinkedHashMap` out of START_ARRAY token异常。

　　经过修改后的前端代码如下所示：

        // 获取分页数据
        findPage: function (data) {
            if(data !== null) {
                this.pageRequest = data.pageRequest
            }
            
            this.pageRequest.params = {name:'name', value:this.filters.name};
            this.$api.user.findPage(this.pageRequest).then((res) => {
                this.pageResult = res.data
                this.findUserRoles()
            }).then(data!=null?data.callback:'')
        }

 

参考链接：Can not deserialize instance of java.util.LinkedHashMap out of START_ARRAY token