spring
JdbcTemplate

introduzione

Metodi di query di base

Alcuni dei metodi queryFor * disponibili in JdbcTemplate sono utili per semplici istruzioni SQL che eseguono operazioni CRUD.

Interrogazione per data

String sql = "SELECT create_date FROM customer WHERE customer_id = ?";
int storeId = jdbcTemplate.queryForObject(sql, java.util.Date.class, customerId);

Interrogazione per intero

String sql = "SELECT store_id FROM customer WHERE customer_id = ?";
int storeId = jdbcTemplate.queryForObject(sql, Integer.class, customerId);    

O

String sql = "SELECT store_id FROM customer WHERE customer_id = ?";
int storeId = jdbcTemplate.queryForInt(sql, customerId);                 //Deprecated in spring-jdbc 4

Interrogazione per stringa

String sql = "SELECT first_Name FROM customer WHERE customer_id = ?";
String firstName = jdbcTemplate.queryForObject(sql, String.class, customerId);

Interrogare per la lista

String sql = "SELECT first_Name FROM customer WHERE store_id =  ?";
List<String> firstNameList = jdbcTemplate.queryForList(sql, String.class, storeId);

Query per Elenco di mappe

int storeId = 1;
DataSource dataSource = ... //
JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);
String sql = "SELECT * FROM customer WHERE store_id = ?";
List<Map<String, Object>> mapList = jdbcTemplate.queryForList(sql, storeId);

for(Map<String, Object> entryMap : mapList)
{
  for(Entry<String, Object> entry : entryMap.entrySet())
  {
       System.out.println(entry.getKey() + " / " + entry.getValue());
  }
  System.out.println("---");
}

SqlRowSet

DataSource dataSource = ... //
JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);
String sql = "SELECT * FROM customer";
SqlRowSet rowSet = jdbcTemplate.queryForRowSet(sql);

while(rowSet.next())
{
  String firstName = rowSet.getString("first_name");
  String lastName = rowSet.getString("last_name");
  System.out.println("Vorname: " + firstName);
  System.out.println("Nachname: " + lastName);
  System.out.println("---”);
}

O

String sql = "SELECT * FROM customer";
List<Customer> customerList = jdbcTemplate.query(sql, new RowMapper<Customer>()    {

  @Override
  public Customer mapRow(ResultSet rs, int rowNum) throws SQLException
  {
    Customer customer = new Customer();
    customer.setFirstName(rs.getString("first_Name"));
    customer.setLastName(rs.getString("first_Name"));
    customer.setEmail(rs.getString("email"));
 
    return customer;
  }

});

Operazioni batch

JdbcTemplate fornisce anche metodi convenienti per eseguire operazioni batch.

Inserto batch

final ArrayList<Student> list = // Get list of students to insert..
String sql = "insert into student (id, f_name, l_name, age, address) VALUES (?, ?, ?, ?, ?)"
jdbcTemplate.batchUpdate(sql, new BatchPreparedStatementSetter(){
    @Override
    public void setValues(PreparedStatement ps, int i) throws SQLException {
        Student s = l.get(i);
        ps.setString(1, s.getId());
        ps.setString(2, s.getF_name());
        ps.setString(3, s.getL_name());
        ps.setInt(4, s.getAge());
        ps.setString(5, s.getAddress());
    }
    
    @Override
    public int getBatchSize() {
        return l.size();
    }
});

Aggiornamento batch

final ArrayList<Student> list = // Get list of students to update..
String sql = "update student set f_name = ?, l_name = ?, age = ?, address = ? where id = ?"
jdbcTemplate.batchUpdate(sql, new BatchPreparedStatementSetter(){
    @Override
    public void setValues(PreparedStatement ps, int i) throws SQLException {
        Student s = l.get(i);
        ps.setString(1, s.getF_name());
        ps.setString(2, s.getL_name());
        ps.setInt(3, s.getAge());
        ps.setString(4, s.getAddress());
        ps.setString(5, s.getId());
    }
    
    @Override
    public int getBatchSize() {
        return l.size();
    }
});

Esistono ulteriori metodi di batchUpdate che accettano List of object array come parametri di input. Questi metodi utilizzano internamente BatchPreparedStatementSetter per impostare i valori dall'elenco di array nell'istruzione sql.

NamedParameterJdbcTemplate estensione di JdbcTemplate

La classe NamedParameterJdbcTemplate aggiunge il supporto per la programmazione delle istruzioni JDBC utilizzando i parametri denominati, anziché la programmazione delle istruzioni JDBC utilizzando solo gli argomenti classici segnaposto ('?'). La classe NamedParameterJdbcTemplate wrapping di un oggetto JdbcTemplate e delega al JdbcTemplate spostato per svolgere gran parte del proprio lavoro.

DataSource dataSource = ... //
NamedParameterJdbcTemplate jdbcTemplate = new NamedParameterJdbcTemplate(dataSource);

String sql = "SELECT count(*) FROM customer WHERE city_name=:cityName";
Map<String, String> params = Collections.singletonMap("cityName", cityName);
int count = jdbcTemplate.queryForObject(sql, params, Integer.class);