jpa抓取策略详解fetch(lazy ,eager)
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在jpa中jpa默认的加载方式是lazy方式也就是在实际使用到数据的时候才加载相关数据，使用lazy时可以不用显示注明fetch=FetchType.LAZY
实体bean：carage
Java代码
package com.hibernate.jpa.bean1;
import java.util.HashSet;
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;
@Entity
public class Garage {
/**
* many to one 多对一
*/
private Integer gid;
private String garagenum;
private Set<Auto> autos = new HashSet<Auto>();
@Id @GeneratedValue
public Integer getGid() {
return gid;
}
public void setGid(Integer gid) {
this.gid = gid;
}
@Column(length=20)
public String getGaragenum() {
return garagenum;
}
public void setGaragenum(String garagenum) {
this.garagenum = garagenum;
}
@OneToMany(cascade={CascadeType.PERSIST},mappedBy="garage")
public Set<Auto> getAutos() {
return autos;
}
public void setAutos(Set<Auto> autos) {
this.autos = autos;
}
public void addGarageAuto(Auto auto) {
auto.setGarage(this);
this.autos.add(auto);
}
}
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