无法访问实体类中的字段

Question

import java.io.Serializable;
import javax.persistence.*;


/**
 * The persistent class for the "city" database table.
 * 
 */
@Entity
@Table(name="\"city\"")
@NamedQuery(name="City.findAll", query="SELECT c FROM City c")
public class City extends com.dozie.example.util.Entity implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="\"id\"")
    private Integer id;

    @Column(name="\"country_id\"")
    private int countryId;

    @Column(name="\"name\"")
    private String name;

    //bi-directional many-to-one association to Country
    @ManyToOne
    @JoinColumns({
        @JoinColumn(name="\"country_id\"", referencedColumnName="\"id\"")
        })
    private Country country;

    public City() {
    }

    public Integer getId() {
        return this.id;
    }

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

    public int getCountryId() {
        return this.countryId;
    }

    public void setCountryId(int countryId) {
        this.countryId = countryId;
    }

    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Country getCountry() {
        return this.country;
    }

    public void setCountry(Country country) {
        this.country = country;
    }

}

对于我的另一个实体类

import java.io.Serializable;
import javax.persistence.*;
import java.util.Set;


/**
 * The persistent class for the "country" database table.
 * 
 */
@Entity
@Table(name="\"country\"")
@NamedQuery(name="Country.findAll", query="SELECT c FROM Country c")
public class Country extends com.dozie.example.util.Entity implements Serializable {
    private static final long serialVersionUID = 1L;
    private Integer id;
    private String name;
    private Set<City> cities;

    public Country() {
    }


    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="\"id\"")
    public Integer getId() {
        return this.id;
    }

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


    @Column(name="\"name\"")
    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }


    //bi-directional many-to-one association to City
    @OneToMany(mappedBy="country")
    public Set<City> getCities() {
        return this.cities;
    }

    public void setCities(Set<City> cities) {
        this.cities = cities;
    }

    public City addCity(City city) {
        getCities().add(city);
        city.setCountry(this);

        return city;
    }

    public City removeCity(City city) {
        getCities().remove(city);
        city.setCountry(null);

        return city;
    }

}

这是我的数据库表的脚本，它是一个Postgres数据库

CREATE TABLE city
(
  id integer NOT NULL,
  country_id integer NOT NULL,
  name character varying(30) NOT NULL,
  CONSTRAINT city_pk PRIMARY KEY (id),
  CONSTRAINT city_country_fk FOREIGN KEY (country_id)
      REFERENCES country (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE CASCADE,
  CONSTRAINT city_name_idx UNIQUE (name)
)

CREATE TABLE country
(
  id integer NOT NULL,
  name character varying(10) NOT NULL,
  CONSTRAINT country_pk PRIMARY KEY (id),
  CONSTRAINT country_name_idx UNIQUE (name)
)

当我的服务器运行时，我会收到以下错误消息

我会很感激你帮我的忙的。

Answer 1

你到处都加了双引号。你不应该。例如,

 @Table(name="\"city\"")

应该是

@Table(name="city")

而且

@Column(name="\"id\"")

@Column(name="id")

@JoinColumns({
    @JoinColumn(name="\"country_id\"", referencedColumnName="\"id\"")
    })

@JoinColumn(name="country_id")