Hibernate hql 查詢 指定欄位 並獲取結果集
1. 查詢整個對映物件所有欄位
Java程式碼
//直接from查詢出來的是一個對映物件,即:查詢整個對映物件所有欄位
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());
}
輸出結果為:
name1 : password1 : 1
name2 : password2 : 2
name3 : password3 : 3
2.查詢單個欄位
Java程式碼
//查詢單個欄位
String hql = " select name from Users";
Query query = session.createQuery(hql);
List<String> list = query.list();
for(String str : list){
System.out.println(str);
}
輸出結果為:
name1
name2
name3
3.查詢其中幾個欄位
Java程式碼
//查詢其中幾個欄位
String hql = " select name,passwd from Users";
Query query = session.createQuery(hql);
//預設查詢出來的list裡存放的是一個Object陣列
List<Object[]> list = query.list();
for(Object[] object : list){
String name = (String)object[0];
String passwd = (String)object[1];
System.out.println(name + " : " + passwd);
}
輸出結果為:
name1 : password1
name2 : password2
name3 : password3
4.修改預設查詢結果(query.list())不以Object[]陣列形式返回,以List形式返回
引用
//查詢其中幾個欄位,新增new list(),注意list裡的l是小寫的。也不需要匯入包,這樣通過query.list()出來的list裡存放的不再是預設的Object陣列了,而是List集合了
String hql = " select new list(name,passwd) from Users";
Query query = session.createQuery(hql);
//預設查詢出來的list裡存放的是一個Object陣列,但是在這裡list裡存放的不再是預設的Object陣列了,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);
}
/**
輸出結果為:
name1 : password1
name2 : password2
name3 : password3
*/
5.修改預設查詢結果(query.list())不以Object[]陣列形式返回,以Map形式返回
Java程式碼 收藏程式碼
//查詢其中幾個欄位,新增new map(),注意map裡的m是小寫的。也不需要匯入包,這樣通過query.list()出來的list裡存放的不再是預設的Object陣列了,而是map集合了
String hql = " select new map(name,passwd) from Users";
Query query = session.createQuery(hql);
//預設查詢出來的list裡存放的是一個Object陣列,但是在這裡list裡存放的不再是預設的Object陣列了,而是Map集合了
List<Map> list = query.list();
for(Map user : list){
//一條記錄裡所有的欄位值都是map裡的一個元素,key是字串0,1,2,3....,value是欄位值
//如果將hql改為:String hql = " select new map(name as username,passwd as password) from Users";,那麼key將不是字串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...是字串,而不是整形
String passwd = (String)user.get("1");
System.out.println(name + " : " + passwd);
}
/**
輸出結果為:
name1 : password1
name2 : password2
name3 : password3
*/
6.修改預設查詢結果(query.list())不以Object[]陣列形式返回,以Set形式返回,但是因為Set裡是不允許有重複的元素,所以:username和password的值不能相同。只需將hql改為:String hql = " select new set(name,passwd) from Users";
7.修改預設查詢結果(query.list())不以Object[]陣列形式返回,以自定義型別返回
自定義類:
Java程式碼
package com.domain;
public class MyUser {
private String username;
private String password;
//因為:String hql = " select new com.domain.MyUser(name,passwd) from Users";所以必須要有接受2個引數的建構函式
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程式碼
//通過query.list()出來的list裡存放的不再是預設的Object陣列了,而是自定義的類MyUser,必須加包名,String hql = "from Users";中的Users類也是必須加包名的,但是因為再Users.hbm.xml裡<hibernate-mapping auto-import="true"> auto-import預設值為true(所以auto-import屬性也可以不寫),自動匯入了
String hql = " select new com.domain.MyUser(name,passwd) from Users";
Query query = session.createQuery(hql);
//預設查詢出來的list裡存放的是一個Object陣列,但是在這裡list裡存放的不再是預設的Object陣列了,而是MyUser物件了
List<MyUser> myUsers = query.list();
for(MyUser myUser : myUsers){
String name = myUser.getUsername();
String passwd = myUser.getPassword();
System.out.println(name + " : " + passwd);
}
/**
輸出結果為:
name1 : password1
name2 : password2
name3 : password3
*/
8:條件查詢
Java程式碼
//條件查詢,引數索引值從0開始,索引位置。通過setString,setParameter設定引數
String hql = "from Users where name=? and passwd=?";
Query query = session.createQuery(hql);
//第1種方式
// query.setString(0, "name1");
// query.setString(1, "password1");
//第2種方式
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程式碼
//條件查詢,自定義索引名(引數名):username,:password.通過setString,setParameter設定引數
String hql = "from Users where name=:username and passwd=:password";
Query query = session.createQuery(hql);
//第1種方式
// query.setString("username", "name1");
// query.setString("password", "password1");
//第2種方式,第3個引數確定型別
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());
}
還有一種屬於sql方式,但是可以轉化過來entity
相信用過hibernate的兄弟們都會因為多表複雜查詢後,為返回的結果如何組裝到一個VO中而煩惱不已。我也不停的為此而煩惱,但是在看了hibernate的transform後,感覺這個方法還挺管用的。
例如現在有兩張表,一張是user表,放了一些使用者的資訊,另外一張表是使用者發表的帖子,裡邊有一個user的外來鍵。我們需要查詢出來,某個人釋出的帖子,sql如下:
- select u.userName,p.title,p.addTime from user as u,post as p where u.id=p.userId
但是我們的POJO對映僅僅是做了user,post表的對映,這個時候,我們需要寫一個PostVO類,裡邊放著了使用者的資訊和帖子的資訊的屬性,設定get\set方法,務必保證這個類裡邊有一個預設的建構函式。
然後我們開始寫這個資料庫操作的dao,程式碼如下:
- String sql = "select u.userName as <span style="color: #ff0000;">userName </span><span style="color: #000000;">,</span>p.title as <span style="color: #ff0000;">title </span>,p.addTime as <span style="color: #ff0000;">addTime</span> from user as u,post as p where u.id=p.userId"
- Query q = factory.getCurrentSession().createSQLQuery(sql).setResultTransformer(Transformers.aliasToBean(PostVO.class));
紅字部分必須跟PostVO中的屬性一直,這樣就可以返回一個針對PostVO的一個集合。
其實大家可以看下hibernate這一部分的原始碼就會發現,主要是使用了AliasToBeanResultTransformer這個類,通過sql的查詢,會返回陣列,然後hibernate根據資料表的對映,自動幫我們來set對應的欄位屬性,所以標紅的部分務必要跟VO中的屬性值一直,要不然會報錯的。
如果需要的話,大家也可以重寫這個類。例如VOResultTransformer。然後在dao中更改成
- setResultTransformer(new VOResultTransformer(PostVO.class));
即可。
Java程式碼
//條件查詢,通過setProperties設定引數
String hql = "from Users where name=:username and passwd=:password";
Query query = session.createQuery(hql);
//MyUser類的2個屬性必須和:username和:password對應
MyUser myUser = new MyUser("name1","password1");
query.setProperties(myUser);
List<Users> list = query.list();
for(Users users : list){
System.out.println(users.getId());
}
[java] view plaincopy
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;
else
this.ifDefault = ifDefault;
}
@Override
public 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;
}
@Override
public 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;
}
@Override
public String toString() {
return "StationUser [id=" + id + ", username=" + username
+ ", officePhone=" + officePhone + ", mobilePhone1="
+ mobilePhone1 + ", officeEmail=" + officeEmail
+ ", ifDefault=" + ifDefault + "]";
}
Hibernate hql 查詢指定欄位並獲取結果集
}
[java] view plaincopy
@Override
public 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;
}