使用QueryRunner报错：java.sql.SQLException: Cannot create

在使用QueryRunner转换查询结果的时候：

QueryRunner qr = new QueryRunner();
List<Book> list = qr.query(sql, new BeanListHandler<Book>(Book.class));

报错

java.sql.SQLException: Cannot create Book

原因

没给Book类写​​无参构造函数​​，加上之后就好了

创建的完整Book类

public class Book {
    private int bid;
    private String bname;
    private float price;
    private int category;

    public Book() {
    }

    public int getBid() {
        return bid;
    }

    public void setBid(int bid) {
        this.bid = bid;
    }

    public String getBname() {
        return bname;
    }

    public void setBname(String bname) {
        this.bname = bname;
    }

    public float getPrice() {
        return price;
    }

    public void setPrice(float price) {
        this.price = price;
    }
    public int getCategory() {
        return category;
    }

    public void setCategory(int category) {
        this.category = category;
    }
}