Error querying database. Cause: java.lang.IndexOutOfBoundsException: Index: 6, Size: 6

项目突然报这个错误，研究半天，找到解决办法。

项目请求获取token接口，如下提示。

 查看后端报错详细信息。贴出一段比价有价值的报错信息

Caused by: org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.IndexOutOfBoundsException: Index: 6, Size: 6
### The error may exist in file [D:\IDEAWORKSPACE\YJFDataPlatform\yjf-server\target\classes\mapper\TsysAccountMapper.xml]
### The error may involve com.cn.yjf.server.dao.TsysAccountMapper.selectByName
### The error occurred while handling results
### SQL: select                       account_id, user_id, username, password, status, active               from t_sys_account          WHERE  username = ?          limit 1
### Cause: java.lang.IndexOutOfBoundsException: Index: 6, Size: 6
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:153)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:145)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:76)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:427)
	... 115 more

1. 根据报错信息，仔细检查了下sql，发现sql没有问题。
2. 在mapper中定义的返回结果，如果是具体的实体类，该实体类必须要包含一个无参构造器，如果自定义了构造函数，则必须加上无参构造函数。
3. 对实体类加上无参构造函数，问题就解决了。

package com.cn.yjf.server.auth.entity;

import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableName;
import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.userdetails.UserDetails;

import java.io.Serializable;
import java.util.Collection;
import java.util.List;

/**
 * 用户信息表实体
 */
@TableName("t_sys_account")
public class TsysAccount implements Serializable, UserDetails {

    private Long accountId; //主键ID
    private Long userId; //用户编号
    private String username; //用户名称
    private String password; //密码
    private Integer status; //状态 1-正常
    private Integer active; //1-正常；0-禁用
    @TableField(exist = false)
    List roles; //角色集合
    @TableField(exist = false)
    private List authorities; //权限集合

    public TsysAccount() {}

    public TsysAccount(Long accountId, Long userId, String username, String password, Integer status, Integer active, List roles, List authorities) {
        this.accountId = accountId;
        this.userId = userId;
        this.username = username;
        this.password = password;
        this.status = status;
        this.active = active;
        this.roles = roles;
        this.authorities = authorities;
    }

    public Long getAccountId() {
        return accountId;
    }

    public void setAccountId(Long accountId) {
        this.accountId = accountId;
    }

    public Long getUserId() {
        return userId;
    }

    public void setUserId(Long userId) {
        this.userId = userId;
    }

    public String getUsername() {
        return username;
    }

    @Override
    public boolean isAccountNonExpired() {
        return true;
    }

    @Override
    public boolean isAccountNonLocked() {
        if (this.status == null) {
            return false;
        } else {
            return this.status.equals(1);
        }
    }

    @Override
    public boolean isCredentialsNonExpired() {
        return true;
    }

    @Override
    public boolean isEnabled() {
        if(this.active==0){
            return false;
        }else{
            return true;
        }
    }
    @Override
    public Collection getAuthorities() {
        return this.authorities;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Integer getStatus() {
        return status;
    }

    public void setStatus(Integer status) {
        this.status = status;
    }

    public Integer getActive() {
        return active;
    }

    public void setActive(Integer active) {
        this.active = active;
    }

    public List getRoles() {
        return roles;
    }

    public void setRoles(List roles) {
        this.roles = roles;
    }

    public void setAuthorities(List authorities) {
        this.authorities = authorities;
    }
}