添加：save(对象)
删除：delete（主键或者带有主键的对象）
修改：save（对象）
对象中没有id，执行添加操作
对象中有id
id不存在：执行添加
id存在：
其余数据与数据库中一致，只发送查询
其余数据与数据库中不一致，发送更新语句
查询
查询某一个findOne（主键） 及时加载
查询某一个getOne(主键) 懒加载
使用过程中会报no session问题，需要追加@Transactional
查询某一个findOne（动态参数）
@Test
public void find() {
Specification<User> spec = new Specification<User>() {
@Override
public Predicate toPredicate(Root<User> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder cb) {
Path<Object> username = root.get("username");
Path<Object> id = root.get("id");
Path<Object> age = root.get("age");
Predicate p1 = cb.equal(username, 1111);
Predicate p2 = cb.equal(id, 1);
Predicate p3 = cb.equal(age, 18);
Predicate[] ps = new Predicate[3];
ps[0] = p1;
ps[1] = p2;
ps[2] = p3;
Predicate predicate = cb.and(ps);
return predicate;
}
};
User user = userDao.findOne(spec);
System.out.println(user);
}查询所有findAll（）
查询所有并排序findAll（sort）
Sort sort = new Sort(Sort.Direction.DESC,"id");
List<User> userList = userdao.findAll(sort);查询所有并分页findAll（pageable）
Pageable pageable = new PageRequest(0,5);
Page<User> page = userdao.findAll(pageable);动态查询所有并分页findAll（动态参数,pageable）
参考查询某一个findOne（动态参数）
动态查询所有并排序findAll（动态参数,sort）
参考查询某一个findOne（动态参数）
通过JPQL语句个性化查询
//通过用户名查询
@Query("from User where username=?1")
User test01(String username);
//通过用户名、密码登录
@Query("from User where username=?1 and password = ?2")
User login(String username,String password);
//通过id搜索用户名
@Query("select username from User where id=?1")
User test02(int id);通过SQL个性化查询
@Query(value = "select username from User where id=?1",nativeQuery = true)
User test03(int id);通过个性化方法名称査询 find+By+属性名称+And+....
User findByUsernameAndPassword(string username,string password);
List<User> findTop5ByUsername(string username);
User findByUsernameLike(string username):关联关系
一对多
从多查一:默认及时加载，发送一条 sql 语句
从一査多:默认懒加载，发送多条sql语句，报错
解决方式一:追加@Transactional
解决方式二:开启及时加载
package com.xszx.beans;
import javax.persistence.*;
@Entity
@Table(name = "t_user")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String username;
private String password;
private int age;
/**
* @ManyToOne 多对一
* 属性targetEntity：对方的字节码
* @JoinColumn 加入列名
* 属性name：列的名称
* 属性referencedColumnName：对方表的主键列名
*/
@ManyToOne(targetEntity = Group.class)
@JoinColumn(name = "gid",referencedColumnName = "gid")
private Group group;
public Group getGroup() {
return group;
}
public void setGroup(Group group) {
this.group = group;
}
public User() {
}
public User(int id, String username, String password, int age) {
this.id = id;
this.username = username;
this.password = password;
this.age = age;
}
public User(int age, String password, String username) {
this.age = age;
this.password = password;
this.username = username;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
", age=" + age +
'}';
}
}
package com.xszx.beans;
import javax.persistence.*;
import java.util.List;
@Entity
@Table(name = "t_group")
public class Group {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int gid;
private String gname;
/**
* @OneToMany 一对多
* 属性targetEntity：对方字节码
* 属性mappedBy：对方实体类中，对方属性名，关系由对方维护
* 属性fetch：配置懒加载与及时加载
* */
@OneToMany(targetEntity = User.class,mappedBy = "group",fetch = FetchType.EAGER)
private List<User> users;
public List<User> getUsers() {
return users;
}
public void setUsers(List<User> users) {
this.users = users;
}
public Group() {
}
public Group(int gid, String gname) {
this.gid = gid;
this.gname = gname;
}
public int getGid() {
return gid;
}
public void setGid(int gid) {
this.gid = gid;
}
public String getGname() {
return gname;
}
public void setGname(String gname) {
this.gname = gname;
}
@Override
public String toString() {
return "Group{" +
"gid=" + gid +
", gname='" + gname + '\'' +
'}';
}
}多对多
package com.xszx.beans;
import javax.persistence.*;
import java.util.List;
@Entity
@Table(name = "t_student")
public class Student {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int sid;
private String sname;
/**
* @ManyToMany 多对多
* 属性targetEntity：对方的字节码
* @joinTable 加入中间表
* 属性name：中间表名
* 属性joinColumns：本类在中间表的字段
* 属性inverseJoinColumns：对方在中间表的字段
*/
@ManyToMany(targetEntity = Teacher.class)
@JoinTable(name = "t_stu_tea",
joinColumns = {@JoinColumn(name = "sid",referencedColumnName = "sid")},
inverseJoinColumns = {@JoinColumn(name = "tid",referencedColumnName = "tid")})
private List<Teacher> teachers;
public List<Teacher> getTeachers() {
return teachers;
}
public void setTeachers(List<Teacher> teachers) {
this.teachers = teachers;
}
public Student() {
}
public Student(int sid, String sname) {
this.sid = sid;
this.sname = sname;
}
public int getSid() {
return sid;
}
public void setSid(int sid) {
this.sid = sid;
}
public String getSname() {
return sname;
}
public void setSname(String sname) {
this.sname = sname;
}
@Override
public String toString() {
return "Student{" +
"sid=" + sid +
", sname='" + sname + '\'' +
'}';
}
}
package com.xszx.beans;
import javax.persistence.*;
import java.util.List;
@Entity
@Table(name = "t_teacher")
public class Teacher {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int tid;
private String tname;
@ManyToMany(targetEntity = Student.class,mappedBy = "teachers")
private List<Student> students;
public Teacher() {
}
public Teacher(int tid, String tname) {
this.tid = tid;
this.tname = tname;
}
public List<Student> getStudents() {
return students;
}
public void setStudents(List<Student> students) {
this.students = students;
}
public int getTid() {
return tid;
}
public void setTid(int tid) {
this.tid = tid;
}
public String getTname() {
return tname;
}
public void setTname(String tname) {
this.tname = tname;
}
@Override
public String toString() {
return "Teacher{" +
"tid=" + tid +
", tname='" + tname + '\'' +
'}';
}
}