如何從JDBC檢索序列元數據？

Question

我想從Java代碼（使用基本的JDBC）檢索我的Oracle數據庫的不同類型的元數據。例如，如果我想與_FOO後綴檢索表的列表，我可以這樣做：

Connection connection = dataSource.getConnection(); 
DatabaseMetaData meta = connection.getMetaData(); 
ResultSet tables = meta.getTables(connection.getCatalog(), null, "%_FOO", new String[] { "TABLE" }); 
// Iterate on the ResultSet to get information on tables... 

現在，我想從我的數據庫檢索所有序列（例如所有序列命名爲S_xxx_FOO ）。

我將如何做到這一點，因爲我沒有看到DatabaseMetaData任何有關序列？

我一定要運行像select * from user_sequences查詢？

Answer 1

您無法通過JDBC API做到這一點，因爲一些數據庫（仍然）不支持序列。

，讓他們的唯一方法是查詢您的DBMS（我想這是甲骨文在你的情況你提到user_sequences）

Answer 2

有同樣問題的系統目錄。這很容易。只需將「SEQUENCE」傳遞給getMetaData（）。getTables（）類型參數即可。

在特定情況下，它會是這樣的：

meta.getTables（connection.getCatalog（），NULL， 「％_Foo」，新的String [] { 「序列」}）;

Answer 3

您可以使用Hibernate的方言API檢索序列名稱。見：http://docs.jboss.org/hibernate/orm/3.2/api/org/hibernate/dialect/Dialect.html

從下面的例子，你可以看到如何使用方言來獲得序列名稱

public static void main(String[] args) { 
     Connection jdbcConnection = null; 
     try { 
      jdbcConnection = DriverManager.getConnection("", "", ""); 
      printAllSequenceName(jdbcConnection); 
     } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } finally { 
      if(jdbcConnection != null) { 
       try { 
        jdbcConnection.close(); 
       } catch (SQLException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 
      } 
     } 
} 

public static void printAllSequenceName(Connection conn) throws JDBCConnectionException, SQLException { 
     DialectResolver dialectResolver = new StandardDialectResolver(); 
     Dialect dialect = dialectResolver.resolveDialect(conn.getMetaData()); 

     if (dialect.supportsSequences()) { 
      String sql = dialect.getQuerySequencesString(); 
      if (sql!=null) { 

       Statement statement = null; 
       ResultSet rs = null; 
       try { 
        statement = conn.createStatement(); 
        rs = statement.executeQuery(sql); 

        while (rs.next()) { 
         System.out.println("Sequence Name : " + rs.getString(1)); 
        } 
       } 
       finally { 
        if (rs!=null) rs.close(); 
        if (statement!=null) statement.close(); 
       } 

      } 
     } 
    } 

如果你不希望使用休眠，那麼你必須箱定製順序具體實施。對於自定義實現

示例代碼

interface SequenceQueryGenerator { 
    String getSelectSequenceNextValString(String sequenceName); 
    String getCreateSequenceString(String sequenceName, int initialValue, int incrementSize); 
    String getDropSequenceStrings(String sequenceName); 
    String getQuerySequencesString(); 
} 


class OracleSequenceQueryGenerator implements SequenceQueryGenerator { 

    @Override 
    public String getSelectSequenceNextValString(String sequenceName) { 
     return "select " + getSelectSequenceNextValString(sequenceName) + " from dual"; 
    } 

    @Override 
    public String getCreateSequenceString(String sequenceName, 
      int initialValue, int incrementSize) { 
     return "create sequence " + sequenceName + " start with " + initialValue + " increment by " + incrementSize; 
    } 

    @Override 
    public String getDropSequenceStrings(String sequenceName) { 
     return "drop sequence " + sequenceName; 
    } 

    @Override 
    public String getQuerySequencesString() { 
     return "select sequence_name from user_sequences"; 
    } 

} 


class PostgresSequenceQueryGenerator implements SequenceQueryGenerator { 

    @Override 
    public String getSelectSequenceNextValString(String sequenceName) { 
     return "select " + getSelectSequenceNextValString(sequenceName); 
    } 

    @Override 
    public String getCreateSequenceString(String sequenceName, 
      int initialValue, int incrementSize) { 
     return "create sequence " + sequenceName + " start " + initialValue + " increment " + incrementSize; 
    } 

    @Override 
    public String getDropSequenceStrings(String sequenceName) { 
     return "drop sequence " + sequenceName; 
    } 

    @Override 
    public String getQuerySequencesString() { 
     return "select relname from pg_class where relkind='S'"; 
    } 

} 

public void printSequenceName (SequenceQueryGenerator queryGenerator, Connection conn) throws SQLException { 
     String sql = queryGenerator.getQuerySequencesString(); 
     if (sql!=null) { 

      Statement statement = null; 
      ResultSet rs = null; 
      try { 
       statement = conn.createStatement(); 
       rs = statement.executeQuery(sql); 

       while (rs.next()) { 
        System.out.println("Sequence Name : " + rs.getString(1)); 
       } 
      } 
      finally { 
       if (rs!=null) rs.close(); 
       if (statement!=null) statement.close(); 
      } 

     } 
    } 

public static void main(String[] args) { 
     Connection jdbcConnection = null; 
     try { 
      jdbcConnection = DriverManager.getConnection("", "", ""); 
      printAllSequenceName(new OracleSequenceQueryGenerator(), jdbcConnection); 
     } catch (SQLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     }finally { 
      if(jdbcConnection != null) { 
       try { 
        jdbcConnection.close(); 
       } catch (SQLException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 
      } 
     } 
} 

Answer 4

鑑於最近的Oracle JDBC驅動程序（如12.1.0.2）的版本don't return sequence information當你調用DatabaseMetaData#getTables與types設置爲["SEQUENCE"]，最好的辦法是運行必要的查詢自己，如：

SELECT o.owner AS sequence_owner, 
     o.object_name AS sequence_name 
    FROM all_objects o 
    WHERE o.owner LIKE 'someOwnerPattern' ESCAPE '/' 
    AND o.object_name LIKE 'someNamePattern' ESCAPE '/' 
    AND o.object_type = 'SEQUENCE' 
    ORDER BY 1, 2 

...其中someOwnerPattern和someNamePattern就像你與使用的那些SQL模式運營商（例如%匹配任何內容）。

這與驅動程序本身運行的查詢基本相同，只是它查詢SEQUENCE類型的對象。