Hibernate查询重要笔记 - HQL总结数据库各种查询宝典大总结

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1. 查询整个映射对象所有字段

Java代码

//直接from查询出来的是一个映射对象，即：查询整个映射对象所有字段
String hql = "from Users";
Query query = session.createQuery(hql);
List<Users> users = query.list();
for(Users user : users){
System.out.println(user.getName() + " : " + user.getPasswd() + " : " + user.getId());
}
输出结果为：
name1 : password1 : 1
name2 : password2 : 2
name3 : password3 : 3

2.查询单个字段

Java代码

//查询单个字段
String hql = " select name from Users";
Query query = session.createQuery(hql);
List<String> list = query.list();
for(String str : list){
System.out.println(str);
}
输出结果为：
name1
name2
name3

3.查询其中几个字段

Java代码

//查询其中几个字段
String hql = " select name,passwd from Users";
Query query = session.createQuery(hql);
//默认查询出来的list里存放的是一个Object数组
List<Object[]> list = query.list();
for(Object[] object : list){
String name = (String)object[0];
String passwd = (String)object[1];
System.out.println(name + " : " + passwd);
}
输出结果为：
name1 : password1
name2 : password2
name3 : password3

4.修改默认查询结果(query.list())不以Object[]数组形式返回，以List形式返回

引用

//查询其中几个字段,添加new list(),注意list里的l是小写的。也不需要导入包，这样通过query.list()出来的list里存放的不再是默认的Object数组了，而是List集合了
        String hql = " select new list(name,passwd) from Users";
        Query query = session.createQuery(hql);
        //默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是List集合了
        List<List> list = query.list();
        for(List user : list){
            String name = (String)user.get(0);
            String passwd = (String)user.get(1);

            System.out.println(name + " : " + passwd);
        }
        /**
        输出结果为：
         name1 : password1
        name2 : password2
        name3 : password3
         */

5.修改默认查询结果(query.list())不以Object[]数组形式返回，以Map形式返回

Java代码

//查询其中几个字段,添加new map(),注意map里的m是小写的。也不需要导入包，这样通过query.list()出来的list里存放的不再是默认的Object数组了，而是map集合了
String hql = " select new map(name,passwd) from Users";
Query query = session.createQuery(hql);
//默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是Map集合了
List<Map> list = query.list();
for(Map user : list){
//一条记录里所有的字段值都是map里的一个元素,key是字符串0,1,2,3....，value是字段值
//如果将hql改为：String hql = " select new map(name as username,passwd as password) from Users";,那么key将不是字符串0,1,2...了，而是"username","password"了
String name = (String)user.get("0");//get("0");是get(key),注意:0,1,2...是字符串，而不是整形
String passwd = (String)user.get("1");
System.out.println(name + " : " + passwd);
}
/**
输出结果为：
name1 : password1
name2 : password2
name3 : password3
*/

6.修改默认查询结果(query.list())不以Object[]数组形式返回，以Set形式返回,但是因为Set里是不允许有重复的元素，所以:username和password的值不能相同。只需将hql改为：String hql = " select new set(name,passwd) from Users";

7.修改默认查询结果(query.list())不以Object[]数组形式返回，以自定义类型返回

自定义类：

Java代码

package com.domain;
public class MyUser {
private String username;
private String password;
//因为：String hql = " select new com.domain.MyUser(name,passwd) from Users";所以必须要有接受2个参数的构造函数
public MyUser(String username,String password){
this.username = username;
this.password = password;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}

Java代码

//通过query.list()出来的list里存放的不再是默认的Object数组了,而是自定义的类MyUser,必须加包名，String hql = "from Users";中的Users类也是必须加包名的，但是因为再Users.hbm.xml里<hibernate-mapping auto-import="true"> auto-import默认值为true（所以auto-import属性也可以不写）,自动导入了
String hql = " select new com.domain.MyUser(name,passwd) from Users";
Query query = session.createQuery(hql);
//默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是MyUser对象了
List<MyUser> myUsers = query.list();
for(MyUser myUser : myUsers){
String name = myUser.getUsername();
String passwd = myUser.getPassword();
System.out.println(name + " : " + passwd);
}
/**
输出结果为：
name1 : password1
name2 : password2
name3 : password3
*/

8：条件查询

Java代码

//条件查询，参数索引值从0开始，索引位置。通过setString,setParameter设置参数
String hql = "from Users where name=? and passwd=?";
Query query = session.createQuery(hql);
//第1种方式
// query.setString(0, "name1");
// query.setString(1, "password1");
//第2种方式
query.setParameter(0, "name1",Hibernate.STRING);
query.setParameter(1, "password1",Hibernate.STRING);
List<Users> list = query.list();
for(Users users : list){
System.out.println(users.getId());
}

Java代码

//条件查询，自定义索引名(参数名):username,:password.通过setString,setParameter设置参数
String hql = "from Users where name=:username and passwd=:password";
Query query = session.createQuery(hql);
//第1种方式
// query.setString("username", "name1");
// query.setString("password", "password1");
//第2种方式,第3个参数确定类型
query.setParameter("username", "name1",Hibernate.STRING);
query.setParameter("password", "password1",Hibernate.STRING);
List<Users> list = query.list();
for(Users users : list){
System.out.println(users.getId());
}

Java代码

//条件查询,通过setProperties设置参数
String hql = "from Users where name=:username and passwd=:password";
Query query = session.createQuery(hql);
//MyUser类的2个属性必须和:username和:password对应
MyUser myUser = new MyUser("name1","password1");
query.setProperties(myUser);
List<Users> list = query.list();
for(Users users : list){
System.out.println(users.getId());
}

package com.hp.ts.bca.user.bo;import com.hp.ts.bca.common.BaseObject;public class StationUser  extends BaseObject {private static final long serialVersionUID = -1175811459644997844L;private int id;private String username;private String officePhone;private String mobilePhone1;private String officeEmail;private Integer ifDefault;public StationUser(int id, String username, String officePhone,String mobilePhone1, String officeEmail, Integer ifDefault) {super();this.id = id;this.username = username;this.officePhone = officePhone;this.mobilePhone1 = mobilePhone1;this.officeEmail = officeEmail;this.ifDefault = ifDefault;}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getOfficePhone() {return officePhone;}public void setOfficePhone(String officePhone) {this.officePhone = officePhone;}public String getMobilePhone1() {return mobilePhone1;}public void setMobilePhone1(String mobilePhone1) {this.mobilePhone1 = mobilePhone1;}public String getOfficeEmail() {return officeEmail;}public void setOfficeEmail(String officeEmail) {this.officeEmail = officeEmail;}public Integer getIfDefault() {return ifDefault;}public void setIfDefault(Integer ifDefault) {if(ifDefault==null) ifDefault=0;elsethis.ifDefault = ifDefault;}@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + id;result = prime * result+ ((ifDefault == null) ? 0 : ifDefault.hashCode());result = prime * result+ ((mobilePhone1 == null) ? 0 : mobilePhone1.hashCode());result = prime * result+ ((officeEmail == null) ? 0 : officeEmail.hashCode());result = prime * result+ ((officePhone == null) ? 0 : officePhone.hashCode());result = prime * result+ ((username == null) ? 0 : username.hashCode());return result;}@Overridepublic boolean equals(Object obj) {if (this == obj)return true;if (obj == null)return false;if (getClass() != obj.getClass())return false;StationUser other = (StationUser) obj;if (id != other.id)return false;if (ifDefault == null) {if (other.ifDefault != null)return false;} else if (!ifDefault.equals(other.ifDefault))return false;if (mobilePhone1 == null) {if (other.mobilePhone1 != null)return false;} else if (!mobilePhone1.equals(other.mobilePhone1))return false;if (officeEmail == null) {if (other.officeEmail != null)return false;} else if (!officeEmail.equals(other.officeEmail))return false;if (officePhone == null) {if (other.officePhone != null)return false;} else if (!officePhone.equals(other.officePhone))return false;if (username == null) {if (other.username != null)return false;} else if (!username.equals(other.username))return false;return true;}@Overridepublic String toString() {return "StationUser [id=" + id + ", username=" + username+ ", officePhone=" + officePhone + ", mobilePhone1="+ mobilePhone1 + ", officeEmail=" + officeEmail+ ", ifDefault=" + ifDefault + "]";}}

@Overridepublic PageResponse<User> getUserListByStationId(int currentPage,int rowsPerPage, String sidx, String sord, Integer stationId) {StringBuilder hql = new StringBuilder();hql.append("select new com.hp.ts.bca.user.bo.StationUser(a.id,a.username,a.officePhone,a.mobilePhone1,a.officeEmail,ug.ifDefault) FROM User a, UserGroup ug WHERE a.id=ug.userId and ug.groupId=");hql.append(stationId);//hql.append("FROM User AS user, UserGroup AS ug WHERE user.id=ug.userId");PageResponse<User> userList = this.groupDao.excutePage(hql.toString(),currentPage, rowsPerPage, sidx, sord);return userList;}

Hibernate查询重要笔记 - HQL总结 数据库各种查询宝典 大总结

Hibernate查询重要笔记 - HQL总结数据库各种查询宝典大总结