@OneToMany或@ManyToOne的用法-annotation关系映射篇
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 |
Java代码 package com.pandy.ssh4.domian; import java.util.Set; import javax.persistence.CascadeType; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.OneToMany; import javax.persistence.Table; @Entity @Table(name = "ParentOne") public class ParentOne { private int p1Id; private String p1Name; private String p1Desc; private Set<ParentTwo> parentTwos; @Id @GeneratedValue @Column(name = "p1_id", unique = true, nullable = false) public int getP1Id() { return p1Id; } public void setP1Id(int p1Id) { this.p1Id = p1Id; } @Column(name = "p1_name", length = 100, nullable = true) public String getP1Name() { return p1Name; } public void setP1Name(String p1Name) { this.p1Name = p1Name; } @Column(name = "p1_desc", length = 100, nullable = true) public String getP1Desc() { return p1Desc; } public void setP1Desc(String p1Desc) { this.p1Desc = p1Desc; } @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "parentOne") // 这里配置关系，并且确定关系维护端和被维护端。mappBy表示关系被维护端，只有关系端有权去更新外键。 // 这里还有注意OneToMany默认的加载方式是赖加载。当看到设置关系中最后一个单词是Many，那么该加载默认为懒加载 public Set<ParentTwo> getParentTwos() { return parentTwos; } public void setParentTwos(Set<ParentTwo> parentTwos) { this.parentTwos = parentTwos; } } |
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 |
Java代码 package com.pandy.ssh4.domian; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.Table; @Entity @Table(name = "ParentTwo") public class ParentTwo { private int p2Id; private String p2Name; private String p2Remark; private ParentOne parentOne; @Id @GeneratedValue @Column(name = "p2_id", nullable = false, unique = true) public int getP2Id() { return p2Id; } public void setP2Id(int p2Id) { this.p2Id = p2Id; } @Column(name = "p2_name", nullable = true) public String getP2Name() { return p2Name; } public void setP2Name(String p2Name) { this.p2Name = p2Name; } @Column(name = "p2_remark", nullable = true) public String getP2Remark() { return p2Remark; } public void setP2Remark(String p2Remark) { this.p2Remark = p2Remark; } // 这里设置JoinColum设置了外键的名字，并且ParentTwo是关系维护端 @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "p1_id") public ParentOne getParentOne() { return parentOne; } public void setParentOne(ParentOne parentOne) { this.parentOne = parentOne; } } |
