netbeans有一个向导，可以完全按照您的要求执行：
在“项目”面板中，在项目中选择要包含实体类的包。
右键单击并选择new>entity classes from database。。。从上下文菜单。

“从数据库新建实体类”向导将运行。
在“数据库表”页上：

从数据库连接下拉列表中选择要使用的连接。
从“可用表”列表中选择要为其生成实体类的表。
单击add>或add all>按钮将表移动到selected tables列表，然后单击next>按钮。
在“实体类”页面上，选择所需的任何选项，尽管默认值通常是合适的。单击next>按钮。
在“Map选项”页面上，选择所需的任何选项，尽管默认值通常是合适的。单击“完成”按钮。
运行向导后，将在所选包中创建实体类。例如：

/*
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 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package mysql8demo;

import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.xml.bind.annotation.XmlRootElement;

/**
 *
 * @author johndoe
 */
@Entity
@Table(name = "country")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Country.findAll", query = "SELECT c FROM Country c")
    , @NamedQuery(name = "Country.findById", query = "SELECT c FROM Country c WHERE c.id = :id")
    , @NamedQuery(name = "Country.findByCountryCode", query = "SELECT c FROM Country c WHERE c.countryCode = :countryCode")
    , @NamedQuery(name = "Country.findByCountryName", query = "SELECT c FROM Country c WHERE c.countryName = :countryName")
    , @NamedQuery(name = "Country.findByCurrencyCode", query = "SELECT c FROM Country c WHERE c.currencyCode = :currencyCode")
    , @NamedQuery(name = "Country.findByPopulation", query = "SELECT c FROM Country c WHERE c.population = :population")
    , @NamedQuery(name = "Country.findByCapital", query = "SELECT c FROM Country c WHERE c.capital = :capital")
    , @NamedQuery(name = "Country.findByContinent", query = "SELECT c FROM Country c WHERE c.continent = :continent")
    , @NamedQuery(name = "Country.findByAreaInSqKm", query = "SELECT c FROM Country c WHERE c.areaInSqKm = :areaInSqKm")})
public class Country implements Serializable {

    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id")
    private Integer id;
    @Basic(optional = false)
    @Column(name = "countryCode")
    private String countryCode;
    @Basic(optional = false)
    @Column(name = "countryName")
    private String countryName;
    @Column(name = "currencyCode")
    private String currencyCode;
    @Column(name = "population")
    private String population;
    @Column(name = "capital")
    private String capital;
    @Column(name = "continent")
    private String continent;
    @Column(name = "areaInSqKm")
    private Integer areaInSqKm;

    public Country() {
    }

    public Country(Integer id) {
        this.id = id;
    }

    public Country(Integer id, String countryCode, String countryName) {
        this.id = id;
        this.countryCode = countryCode;
        this.countryName = countryName;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getCountryCode() {
        return countryCode;
    }

    public void setCountryCode(String countryCode) {
        this.countryCode = countryCode;
    }

    public String getCountryName() {
        return countryName;
    }

    public void setCountryName(String countryName) {
        this.countryName = countryName;
    }

    public String getCurrencyCode() {
        return currencyCode;
    }

    public void setCurrencyCode(String currencyCode) {
        this.currencyCode = currencyCode;
    }

    public String getPopulation() {
        return population;
    }

    public void setPopulation(String population) {
        this.population = population;
    }

    public String getCapital() {
        return capital;
    }

    public void setCapital(String capital) {
        this.capital = capital;
    }

    public String getContinent() {
        return continent;
    }

    public void setContinent(String continent) {
        this.continent = continent;
    }

    public Integer getAreaInSqKm() {
        return areaInSqKm;
    }

    public void setAreaInSqKm(Integer areaInSqKm) {
        this.areaInSqKm = areaInSqKm;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Country)) {
            return false;
        }
        Country other = (Country) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "mysql8demo.Country[ id=" + id + " ]";
    }

}