hibernate onetomany annotation fetch = FetchType.LAZY不起作用

时间：2016-09-10 02:09:04

标签： java mysql hibernate one-to-many

我有三个表A，B和C。表B具有对表a_id的外键A引用，表B具有对表a_id的外键A引用。我的hibernate实体文件如下：

A.java 

@Entity
@Table(name = "A")
public class A {

    private long id;
    private String contentA;
    private List<B> bList;
    private List<C> cList;

    @OneToMany(fetch = FetchType.EAGER , mappedBy = "b")
    public List<B> getbList() {
        return bList;
    }

    public void setbList(List<B> bList) {
        this.bList = bList;
    }

    @OneToMany(fetch = FetchType.EAGER , mappedBy = "b")
    public List<C> getcList() {
        return cList;
    }

    public void setcList(List<C> cList) {
        this.cList = cList;
    }

    @Id
    @Column(name = "id", nullable = false)
    public long getId() {
        return id;
    }

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

    @Basic
    @Column(name = "content_a", nullable = false, length = 1000)
    public String getContentA() {
        return contentA;
    }

    public void setContentA(String contentA) {
        this.contentA = contentA;
    }
}

B.java 

@Entity
@Table(name = "B")
public class B {

    private long id;
    private String contentB;
    private A a;

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "a_id", nullable = false)
    public A getA() {
        return a;
    }

    public void setA(A a) {
        this.a = a;
    }

    @Id
    @Column(name = "id", nullable = false)
    public long getId() {
        return id;
    }

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

    @Basic
    @Column(name = "content_b", nullable = false, length = 1000)
    public String getContentB() {
        return contentB;
    }

    public void setContentB(String contentB) {
        this.contentB = contentB;
    }

}

C.java 

@Entity
@Table(name = "C")
public class C {

    private long id;
    private String contentC;
    private A a;

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "a_id", nullable = false)
    public A getA() {
        return a;
    }

    public void setA(A a) {
        this.a = a;
    }

    @Id
    @Column(name = "id", nullable = false)
    public long getId() {
        return id;
    }

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

    @Basic
    @Column(name = "content_c", nullable = false, length = 1000)
    public String getContentC() {
        return contentC;
    }

    public void setContentC(String contentC) {
        this.contentC = contentC;
    }

}

问题有时我只想用A获取List<B>，而在另一时间我希望A获得List<C>。我有什么方法可以通过hibernate来做到这一点吗？

------------------------分界线--------------------- -

在我的真实项目中，我有三个实体类：ChapterEntity ChapterTitle1Entity ChapterTitle2Entity ChapterTitle3Entity。 private List<ChapterTitle1Entity> chapterTitle1EntityList;中有ChapterEntity，private List<ChapterTitle2Entity> chapterTitle2EntityList;中ChapterTitle2Entity，private List<ChapterTitle3Entity> chapterTitle3EntityList;中有ChapterTitle2Entity。

我只想获得一个带有子列表ChapterEntity的{​​{1}}列表，延迟加载注释不起作用。以下是我的班级文件

ChapterEntity.java 

List<ChapterTitle1Entity> chapterTitle1EntityList

ChapterTitle1Entity.java 

package com.hnu.tutorial.model.entity;

import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;

import javax.persistence.*;
import java.util.List;

/**
 * Created by shiqin_zhang@qq.com on 2016-09-9/6/16
 * Time 11:16 PM
 */
@Entity
@Table(name = "chapter")
public class ChapterEntity {
    private List<ChapterTitle1Entity> chapterTitle1EntityList;
    private long id;
    private int sequence;
    private String content;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "chapterEntity")
    @Fetch(FetchMode.SUBSELECT)
    public List<ChapterTitle1Entity> getChapterTitle1EntityList() {
        return chapterTitle1EntityList;
    }

    public void setChapterTitle1EntityList(List<ChapterTitle1Entity> chapterTitle1EntityList) {
        this.chapterTitle1EntityList = chapterTitle1EntityList;
    }

    @Id
    @Column(name = "id", nullable = false)
    public long getId() {
        return id;
    }

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

    @Basic
    @Column(name = "sequence", nullable = false)
    public int getSequence() {
        return sequence;
    }

    public void setSequence(int sequence) {
        this.sequence = sequence;
    }

    @Basic
    @Column(name = "content", nullable = false, length = 1000)
    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        ChapterEntity that = (ChapterEntity) o;

        if (id != that.id) return false;
        if (sequence != that.sequence) return false;
        if (content != null ? !content.equals(that.content) : that.content != null) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = (int) (id ^ (id >>> 32));
        result = 31 * result + sequence;
        result = 31 * result + (content != null ? content.hashCode() : 0);
        return result;
    }
}

ChapterTitle2Entity.java 

package com.hnu.tutorial.model.entity;

import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;

import javax.persistence.*;
import java.util.List;

/**
 * Created by shiqin_zhang@qq.com on 2016-09-11
 * Time 6:09 PM
 */
@Entity
@Table(name = "chapter_title_1", schema = "tutorial2")
public class ChapterTitle1Entity {
    private long id;
    private int sequence;
    private String content;
//    private long chapterId;
    /**
     * 1:章前测试，2：实际的测试
     */
    private int type;
    private ChapterEntity chapterEntity;
    private List<ChapterTitle2Entity> chapterTitle2EntityList;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "chapterTitle1Entity")
    @Fetch(FetchMode.SUBSELECT)
    public List<ChapterTitle2Entity> getChapterTitle2EntityList() {
        return chapterTitle2EntityList;
    }

    public void setChapterTitle2EntityList(List<ChapterTitle2Entity> chapterTitle2EntityList) {
        this.chapterTitle2EntityList = chapterTitle2EntityList;
    }

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "chapter_id", nullable = false)
    public ChapterEntity getChapterEntity() {
        return chapterEntity;
    }

    public void setChapterEntity(ChapterEntity chapterEntity) {
        this.chapterEntity = chapterEntity;
    }

    @Id
    @Column(name = "id", nullable = false)
    public long getId() {
        return id;
    }

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

    @Basic
    @Column(name = "sequence", nullable = false)
    public int getSequence() {
        return sequence;
    }

    public void setSequence(int sequence) {
        this.sequence = sequence;
    }

    @Basic
    @Column(name = "content", nullable = false, length = 1000)
    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

/*
    @Basic
    @Column(name = "chapter_id", nullable = false)
    public long getChapterId() {
        return chapterId;
    }

    public void setChapterId(long chapterId) {
        this.chapterId = chapterId;
    }
*/

    @Basic
    @Column(name = "type", nullable = false)
    public int getType() {
        return type;
    }

    public void setType(int type) {
        this.type = type;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        ChapterTitle1Entity that = (ChapterTitle1Entity) o;

        if (id != that.id) return false;
        if (sequence != that.sequence) return false;
//        if (chapterId != that.chapterId) return false;
        if (type != that.type) return false;
        if (content != null ? !content.equals(that.content) : that.content != null) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = (int) (id ^ (id >>> 32));
        result = 31 * result + sequence;
        result = 31 * result + (content != null ? content.hashCode() : 0);
//        result = 31 * result + (int) (chapterId ^ (chapterId >>> 32));
        result = 31 * result + type;
        return result;
    }
}

ChapterTitle3Entity.java 

package com.hnu.tutorial.model.entity;

import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;

import javax.persistence.*;
import java.util.List;

/**
 * Created by shiqin_zhang@qq.com on 2016-09-9/6/16
 * Time 11:16 PM
 */
@Entity
@Table(name = "chapter_title_2")
public class ChapterTitle2Entity {
    private long id;
    private int sequence;
    private String content;
    //    private long title1Id;
    private List<ChapterTitle3Entity> chapterTitle3EntityList;
    private ChapterTitle1Entity chapterTitle1Entity;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "title_1_id", nullable = false)
    public ChapterTitle1Entity getChapterTitle1Entity() {
        return chapterTitle1Entity;
    }

    public void setChapterTitle1Entity(ChapterTitle1Entity chapterTitle1Entity) {
        this.chapterTitle1Entity = chapterTitle1Entity;
    }

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "chapterTitle2Entity")
    @Fetch(FetchMode.SUBSELECT)
    public List<ChapterTitle3Entity> getChapterTitle3EntityList() {
        return chapterTitle3EntityList;
    }

    public void setChapterTitle3EntityList(List<ChapterTitle3Entity> chapterTitle3EntityList) {
        this.chapterTitle3EntityList = chapterTitle3EntityList;
    }

    @Id
    @Column(name = "id", nullable = false)
    public long getId() {
        return id;
    }

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

    @Basic
    @Column(name = "sequence", nullable = false)
    public int getSequence() {
        return sequence;
    }

    public void setSequence(int sequence) {
        this.sequence = sequence;
    }

    @Basic
    @Column(name = "content", nullable = false, length = 1000)
    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

/*
    @Basic
    @Column(name = "title_1_id", nullable = false)
    public long getTitle1Id() {
        return title1Id;
    }

    public void setTitle1Id(long title1Id) {
        this.title1Id = title1Id;
    }
*/

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        ChapterTitle2Entity that = (ChapterTitle2Entity) o;

        if (id != that.id) return false;
        if (sequence != that.sequence) return false;
//        if (title1Id != that.title1Id) return false;
        if (content != null ? !content.equals(that.content) : that.content != null) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = (int) (id ^ (id >>> 32));
        result = 31 * result + sequence;
        result = 31 * result + (content != null ? content.hashCode() : 0);
//        result = 31 * result + (int) (title1Id ^ (title1Id >>> 32));
        return result;
    }
}

我的DAO图层package com.hnu.tutorial.model.entity; import javax.persistence.*; /** * Created by shiqin_zhang@qq.com on 2016-09-9/6/16 * Time 11:16 PM */ @Entity @Table(name = "chapter_title_3") public class ChapterTitle3Entity { private long id; private int sequence; private String content; // private long title2Id; private ChapterTitle2Entity chapterTitle2Entity; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "title_2_id", nullable = false) public ChapterTitle2Entity getChapterTitle2Entity() { return chapterTitle2Entity; } public void setChapterTitle2Entity(ChapterTitle2Entity chapterTitle2Entity) { this.chapterTitle2Entity = chapterTitle2Entity; } @Id @Column(name = "id", nullable = false) public long getId() { return id; } public void setId(long id) { this.id = id; } @Basic @Column(name = "sequence", nullable = false) public int getSequence() { return sequence; } public void setSequence(int sequence) { this.sequence = sequence; } @Basic @Column(name = "content", nullable = false, length = 1000) public String getContent() { return content; } public void setContent(String content) { this.content = content; } /* @Basic @Column(name = "title_2_id", nullable = false) public long getTitle2Id() { return title2Id; } public void setTitle2Id(long title2Id) { this.title2Id = title2Id; } */ @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; ChapterTitle3Entity that = (ChapterTitle3Entity) o; if (id != that.id) return false; if (sequence != that.sequence) return false; if (content != null ? !content.equals(that.content) : that.content != null) return false; return true; } @Override public int hashCode() { int result = (int) (id ^ (id >>> 32)); result = 31 * result + sequence; result = 31 * result + (content != null ? content.hashCode() : 0); return result; } } 

ChapterDAO.java

我的服务层package com.hnu.tutorial.model.dao; import com.hnu.tutorial.model.entity.ChapterEntity; import org.hibernate.Criteria; import org.hibernate.criterion.Order; import org.springframework.stereotype.Repository; import java.util.List; /** * Created by shiqin_zhang@qq.com on 2016-09-9 * Time 11:13 PM */ @Repository public class ChapterDAO extends BaseDAO<ChapterEntity> { public List<ChapterEntity> chapterEntityList(){ Criteria criteria = session().createCriteria(ChapterEntity.class, "chapter"); criteria.createAlias("chapter.chapterTitle1EntityList", "title1List"); criteria.addOrder(Order.desc("title1List.sequence")); List<ChapterEntity> chapterEntityList = criteria.list(); return chapterEntityList; /*String hql = "from ChapterEntity"; List<ChapterEntity> chapterEntityList = session().createQuery(hql).list(); return chapterEntityList;*/ } } 

ChapterSvc

每当我查询章节列表时，我都会得到所有子列表。即使我在服务层的方法package com.hnu.tutorial.service.impl; import com.hnu.tutorial.model.dao.ChapterDAO; import com.hnu.tutorial.model.entity.ChapterEntity; import com.hnu.tutorial.model.entity.ChapterTitle1Entity; import com.hnu.tutorial.service.dto.ChapterDTO; import com.hnu.tutorial.service.dto.ChapterTitle1DTO; import com.hnu.tutorial.service.interfaces.IChapterSvc; import com.hnu.tutorial.utils.BeanMap; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import org.springframework.transaction.annotation.Transactional; import java.util.List; /** * Created by shiqin_zhang@qq.com on 2016-09-10 * Time 10:59 AM */ @Service @Transactional public class ChapterSvc implements IChapterSvc { @Autowired private ChapterDAO chapterDAO; @Override public List<ChapterDTO> chapterDTOList() { List<ChapterEntity> chapterEntityList = chapterDAO.chapterEntityList(); List<ChapterDTO> chapterDTOList = BeanMap.mapList(chapterEntityList, ChapterDTO.class); for(ChapterDTO chapterDTO:chapterDTOList){ List<ChapterTitle1Entity> chapterTitle1EntityList = chapterDTO.getChapterTitle1EntityList(); for (ChapterTitle1Entity chapterTitle1Entity:chapterTitle1EntityList){ chapterTitle1Entity.setChapterEntity(null); } } return chapterDTOList; } } 的末尾设置断点，我也得到所有子列表。我也尝试使用hql查询列表，但它仍然无效。

1 个答案:

答案 0 :(得分：1)

在FetchType.EAGER注释中将FetchType.LAZY更改为@OneToMany。只有当你直接引用它时，这才会让Hibernate加载一个集合。

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