hibernate 懒加载

@Entity @Table(name = "Student") public class StudentInformation { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private int rollno; private String name; // Mapping to the other table @OneToMany(mappedBy ="stud" ,cascade = CascadeType.ALL,fetch=FetchType.LAZY) private Set addressSet=new HashSet<>();; public StudentInformation() { } public StudentInformation(int rollno, String name) { this.rollno = rollno; this.name = name; } public int getRollno() { return rollno; } public void setRollno(int rollno) { this.rollno = rollno; }

@Entity @Table(name = "Address") public class Address { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private int id; private String cityname; @ManyToOne(cascade=CascadeType.ALL) @JoinColumn(name = "Student_id") StudentInformation stud; Address() {} public Address(int id, String cityname, StudentInformation ob1) { this.id = id; this.cityname = cityname; this.stud = ob1; } public int getId() { return id; } public void setId(int id) { this.id = id; }

从code可以看出，

打印第一行，没有用到address， 则hibernate没有执行查询；

打印第二行，用到address，则执行了对address的查询。

通过这个小测试，可以看出来hibernate实现的延迟加载功能。

hibernate对于配置延迟加载的对象进行了监听， 当管理的对象被调用时，立即进行数据加载。