本文介绍了如何在Hibernate中使用本机SQL查询，包括执行基本查询、处理多个表、使用参数以及使用addScalar和addEntity方法。通过示例展示了HibernateSQLQuery的用法和注意事项。
Welcome to the Hibernate Native SQL Query example tutorial. We looked into Hibernate Query Language and Hibernate Criteria in earlier articles, today we will look into Hibernate Native SQL query with examples.
欢迎使用Hibernate Native SQL Query示例教程。 我们在之前的文章中研究了Hibernate Query Language和Hibernate Criteria ，今天我们将通过示例研究Hibernate Native SQL查询。
HibernateSQL查询 (Hibernate SQL Query)
Hibernate provide option to execute native SQL queries through the use of SQLQuery object. Hibernate SQL Query is very handy when we have to execute database vendor specific queries that are not supported by Hibernate API. For example query hints or the CONNECT keyword in Oracle Database.
Hibernate提供了通过使用SQLQuery对象执行本机SQL查询的选项。 当我们必须执行Hibernate API不支持的数据库供应商特定查询时，Hibernate SQL Query非常方便。 例如，查询提示或Oracle数据库中的CONNECT关键字。
For normal scenarios, Hibernate SQL query is not the recommended approach because we loose benefits related to hibernate association and hibernate first level cache.
在正常情况下，不建议使用Hibernate SQL查询，因为我们失去了与hibernate关联和hibernate一级缓存有关的好处。
I will use MySQL database and same tables and data setup as used in HQL example, so you should check out that first to understand the tables and corresponding model classes mapping.
我将使用与HQL示例中使用MySQL数据库以及相同的表和数据设置，因此您应该先检查一下以了解表和对应的模型类映射。
Hibernate本机SQL示例 (Hibernate Native SQL Example)
For Hibernate Native SQL Query, we use Session.createSQLQuery(String query) to create the SQLQuery object and execute it. For example, if you want to read all the records from Employee table, we can do it through below code.
对于Hibernate本机SQL查询，我们使用Session.createSQLQuery(String query)创建SQLQuery对象并执行它。 例如，如果您想从Employee表中读取所有记录，我们可以通过以下代码来完成。
// Prep work
SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
Session session = sessionFactory.getCurrentSession();
// Get All Employees
Transaction tx = session.beginTransaction();
SQLQuery query = session.createSQLQuery("select emp_id, emp_name, emp_salary from Employee");
List<Object[]> rows = query.list();
for(Object[] row : rows){
Employee emp = new Employee();
emp.setId(Long.parseLong(row[0].toString()));
emp.setName(row[1].toString());
emp.setSalary(Double.parseDouble(row[2].toString()));
System.out.println(emp);
}When we execute above code for the data setup we have, it produces following output.
当我们执行以上代码进行数据设置时，将产生以下输出。
Hibernate: select emp_id, emp_name, emp_salary from Employee
Id= 1, Name= Pankaj, Salary= 100.0, {Address= null}
Id= 2, Name= David, Salary= 200.0, {Address= null}
Id= 3, Name= Lisa, Salary= 300.0, {Address= null}
Id= 4, Name= Jack, Salary= 400.0, {Address= null}Notice that list() method returns the List of Object array, we need to explicitly parse them to double, long etc. Our Employee and Address classes have following toString() method implementations.
注意list()方法返回Object数组的List，我们需要显式地将它们解析为double，long等。我们的Employee和Address类具有以下toString()方法实现。
@Override
public String toString() {
return "Id= " + id + ", Name= " + name + ", Salary= " + salary
+ ", {Address= " + address + "}";
}@Override
public String toString() {
return "AddressLine1= " + addressLine1 + ", City=" + city
+ ", Zipcode=" + zipcode;
}Notice that our query is not returning Address data, whereas if we use HQL query "from Employee", it returns the associated table data too.
注意，我们的查询没有返回地址数据，但是如果我们使用HQL查询"from Employee" ，它也会返回关联的表数据。
Hibernate SQL查询addScalar (Hibernate SQL Query addScalar)
Hibernate uses ResultSetMetadata to deduce the type of the columns returned by the query, from performance point of view we can use addScalar() method to define the data type of the column. However we would still get the data in form of Object array.
Hibernate使用ResultSetMetadata来推断查询返回的列的类型，从性能的角度来看，我们可以使用addScalar()方法来定义列的数据类型。 但是，我们仍将以对象数组的形式获取数据。
//Get All Employees - addScalar example
query = session.createSQLQuery("select emp_id, emp_name, emp_salary from Employee")
.addScalar("emp_id", new LongType())
.addScalar("emp_name", new StringType())
.addScalar("emp_salary", new DoubleType());
rows = query.list();
for(Object[] row : rows){
Employee emp = new Employee();
emp.setId(Long.parseLong(row[0].toString()));
emp.setName(row[1].toString());
emp.setSalary(Double.parseDouble(row[2].toString()));
System.out.println(emp);
}The output generated will be same, however we will see slight performance improvement when the data is huge.
生成的输出将相同，但是当数据巨大时我们将看到轻微的性能改进。
Hibernate本机SQL多个表 (Hibernate Native SQL Multiple Tables)
If we would like to get data from both Employee and Address tables, we can simply write the SQL query for that and parse the result set.
如果我们想同时从Employee表和Address表中获取数据，我们可以简单地为此编写SQL查询并解析结果集。
query = session.createSQLQuery("select e.emp_id, emp_name, emp_salary,address_line1, city,
zipcode from Employee e, Address a where a.emp_id=e.emp_id");
rows = query.list();
for(Object[] row : rows){
Employee emp = new Employee();
emp.setId(Long.parseLong(row[0].toString()));
emp.setName(row[1].toString());
emp.setSalary(Double.parseDouble(row[2].toString()));
Address address = new Address();
address.setAddressLine1(row[3].toString());
address.setCity(row[4].toString());
address.setZipcode(row[5].toString());
emp.setAddress(address);
System.out.println(emp);
}For above code, the output produced will be like below.
对于上面的代码，产生的输出将如下所示。
Hibernate: select e.emp_id, emp_name, emp_salary,address_line1, city, zipcode from Employee e, Address a where a.emp_id=e.emp_id
Id= 1, Name= Pankaj, Salary= 100.0, {Address= AddressLine1= Albany Dr, City=San Jose, Zipcode=95129}
Id= 2, Name= David, Salary= 200.0, {Address= AddressLine1= Arques Ave, City=Santa Clara, Zipcode=95051}
Id= 3, Name= Lisa, Salary= 300.0, {Address= AddressLine1= BTM 1st Stage, City=Bangalore, Zipcode=560100}
Id= 4, Name= Jack, Salary= 400.0, {Address= AddressLine1= City Centre, City=New Delhi, Zipcode=100100}Hibernate本机SQL实体和联接 (Hibernate Native SQL Entity and Join)
We can also use addEntity() and addJoin() methods to fetch the data from associated table using tables join. For example, above data can also be retrieved as below.
我们还可以使用addEntity()和addJoin()方法使用表连接从关联表中获取数据。 例如，上面的数据也可以如下检索。
//Join example with addEntity and addJoin
query = session.createSQLQuery("select {e.*}, {a.*} from Employee e join Address a ON e.emp_id=a.emp_id")
.addEntity("e",Employee.class)
.addJoin("a","e.address");
rows = query.list();
for (Object[] row : rows) {
for(Object obj : row) {
System.out.print(obj + "::");
}
System.out.println("\n");
}
//Above join returns both Employee and Address Objects in the array
for (Object[] row : rows) {
Employee e = (Employee) row[0];
System.out.println("Employee Info::"+e);
Address a = (Address) row[1];
System.out.println("Address Info::"+a);
}{[aliasname].*} is used to return all properties of an entity. When we use addEntity() and addJoin() with join queries like above it returns both the objects, as shown above.
{[aliasname].*}用于返回实体的所有属性。 当我们将addEntity()和addJoin()与上面的addJoin()查询一起使用时，它将返回两个对象，如上所示。
Output produced by above code is like below.
上面的代码产生的输出如下。
Hibernate: select e.emp_id as emp_id1_1_0_, e.emp_name as emp_name2_1_0_, e.emp_salary as emp_sala3_1_0_, a.emp_id as emp_id1_0_1_, a.address_line1 as address_2_0_1_, a.city as city3_0_1_, a.zipcode as zipcode4_0_1_ from Employee e join Address a ON e.emp_id=a.emp_id
Id= 1, Name= Pankaj, Salary= 100.0, {Address= AddressLine1= Albany Dr, City=San Jose, Zipcode=95129}::AddressLine1= Albany Dr, City=San Jose, Zipcode=95129::
Id= 2, Name= David, Salary= 200.0, {Address= AddressLine1= Arques Ave, City=Santa Clara, Zipcode=95051}::AddressLine1= Arques Ave, City=Santa Clara, Zipcode=95051::
Id= 3, Name= Lisa, Salary= 300.0, {Address= AddressLine1= BTM 1st Stage, City=Bangalore, Zipcode=560100}::AddressLine1= BTM 1st Stage, City=Bangalore, Zipcode=560100::
Id= 4, Name= Jack, Salary= 400.0, {Address= AddressLine1= City Centre, City=New Delhi, Zipcode=100100}::AddressLine1= City Centre, City=New Delhi, Zipcode=100100::
Employee Info::Id= 1, Name= Pankaj, Salary= 100.0, {Address= AddressLine1= Albany Dr, City=San Jose, Zipcode=95129}
Address Info::AddressLine1= Albany Dr, City=San Jose, Zipcode=95129
Employee Info::Id= 2, Name= David, Salary= 200.0, {Address= AddressLine1= Arques Ave, City=Santa Clara, Zipcode=95051}
Address Info::AddressLine1= Arques Ave, City=Santa Clara, Zipcode=95051
Employee Info::Id= 3, Name= Lisa, Salary= 300.0, {Address= AddressLine1= BTM 1st Stage, City=Bangalore, Zipcode=560100}
Address Info::AddressLine1= BTM 1st Stage, City=Bangalore, Zipcode=560100
Employee Info::Id= 4, Name= Jack, Salary= 400.0, {Address= AddressLine1= City Centre, City=New Delhi, Zipcode=100100}
Address Info::AddressLine1= City Centre, City=New Delhi, Zipcode=100100You can run both the queries in the mysql client and notice that the output produced is same.
您可以在mysql客户端中运行两个查询，并注意产生的输出是相同的。
mysql> select e.emp_id as emp_id1_1_0_, e.emp_name as emp_name2_1_0_, e.emp_salary as emp_sala3_1_0_, a.emp_id as emp_id1_0_1_, a.address_line1 as address_2_0_1_, a.city as city3_0_1_, a.zipcode as zipcode4_0_1_ from Employee e join Address a ON e.emp_id=a.emp_id;
+--------------+----------------+----------------+--------------+----------------+-------------+---------------+
| emp_id1_1_0_ | emp_name2_1_0_ | emp_sala3_1_0_ | emp_id1_0_1_ | address_2_0_1_ | city3_0_1_ | zipcode4_0_1_ |
+--------------+----------------+----------------+--------------+----------------+-------------+---------------+
| 1 | Pankaj | 100 | 1 | Albany Dr | San Jose | 95129 |
| 2 | David | 200 | 2 | Arques Ave | Santa Clara | 95051 |
| 3 | Lisa | 300 | 3 | BTM 1st Stage | Bangalore | 560100 |
| 4 | Jack | 400 | 4 | City Centre | New Delhi | 100100 |
+--------------+----------------+----------------+--------------+----------------+-------------+---------------+
4 rows in set (0.00 sec)
mysql> select e.emp_id, emp_name, emp_salary,address_line1, city, zipcode from Employee e, Address a where a.emp_id=e.emp_id;
+--------+----------+------------+---------------+-------------+---------+
| emp_id | emp_name | emp_salary | address_line1 | city | zipcode |
+--------+----------+------------+---------------+-------------+---------+
| 1 | Pankaj | 100 | Albany Dr | San Jose | 95129 |
| 2 | David | 200 | Arques Ave | Santa Clara | 95051 |
| 3 | Lisa | 300 | BTM 1st Stage | Bangalore | 560100 |
| 4 | Jack | 400 | City Centre | New Delhi | 100100 |
+--------+----------+------------+---------------+-------------+---------+
4 rows in set (0.00 sec)
mysql>具有参数的Hibernate本机SQL查询 (Hibernate Native SQL Query with Parameters)
We can also pass parameters to the Hibernate SQL queries, just like JDBC PreparedStatement. The parameters can be set using the name as well as index, as shown in below example.
我们还可以将参数传递给Hibernate SQL查询，就像JDBC PreparedStatement一样 。 可以使用名称和索引来设置参数，如下例所示。
query = session
.createSQLQuery("select emp_id, emp_name, emp_salary from Employee where emp_id = ?");
List<Object[]> empData = query.setLong(0, 1L).list();
for (Object[] row : empData) {
Employee emp = new Employee();
emp.setId(Long.parseLong(row[0].toString()));
emp.setName(row[1].toString());
emp.setSalary(Double.parseDouble(row[2].toString()));
System.out.println(emp);
}
query = session
.createSQLQuery("select emp_id, emp_name, emp_salary from Employee where emp_id = :id");
empData = query.setLong("id", 2L).list();
for (Object[] row : empData) {
Employee emp = new Employee();
emp.setId(Long.parseLong(row[0].toString()));
emp.setName(row[1].toString());
emp.setSalary(Double.parseDouble(row[2].toString()));
System.out.println(emp);
}Output produced by above code would be:
以上代码产生的输出为：
Hibernate: select emp_id, emp_name, emp_salary from Employee where emp_id = ?
Id= 1, Name= Pankaj, Salary= 100.0, {Address= null}
Hibernate: select emp_id, emp_name, emp_salary from Employee where emp_id = ?
Id= 2, Name= David, Salary= 200.0, {Address= null}That’s all for a brief introduction of Hibernate SQL Query, you should avoid using it unless you want to execute any database specific queries.
这就是Hibernate SQL查询的简要介绍，除非您要执行任何数据库特定的查询，否则应避免使用它。
翻译自: https://www.journaldev.com/3422/hibernate-native-sql-query-example
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