java 连接spark工具类

package com.spark.conn; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import java.sql.*; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; public class SparkConnection { // 查询数据返回json public String getJson(String jdbc_url,String sql) throws SQLException, ClassNotFoundException { Connection connection = null; // org.apache.hive.jdbc.HiveDriver // Class.forName("org.apache.hive.jdbc.HiveDriver"); try { connection = DriverManager.getConnection(jdbc_url); List<Map<String,Object>> list = selectTable(connection,sql); // 想办法把数组转成json ObjectMapper mapper = new ObjectMapper(); return mapper.writeValueAsString(list); } catch (Exception e) { e.printStackTrace(); } finally { if(connection != null) connection.close(); } return null; } // 查询数据返回List public List<Map<String,Object>> getMaps(String jdbc_url,String sql) throws SQLException, ClassNotFoundException { Connection connection = null; //HiveDriver // org.apache.hive.jdbc.HiveDriver // Class.forName("org.apache.hive.jdbc.HiveDriver"); try { connection = DriverManager.getConnection(jdbc_url); return selectTable(connection,sql); } catch (SQLException e) { e.printStackTrace(); } finally { if(connection != null) connection.close(); } return null; } // 执行查询 public List<Map<String,Object>> selectTable(Connection connection,String sql) { //String sql = "select *from wf_process_hive_ro limit 10"; Statement stmt = null; //ResultSet rs = null; try { stmt = connection.createStatement(); ResultSet set = stmt.executeQuery(sql); List<Map<String,Object>> list = new ArrayList<>(); ResultSetMetaData metaData = set.getMetaData(); int columnCount = metaData.getColumnCount(); while(set.next()){ Map<String,Object> map = new HashMap<>(); for (int i = 1; i <= columnCount; ++i) { String columnName = metaData.getColumnName(i).toLowerCase(); Object object = set.getObject(i); map.put(columnName, object); } list.add(map); } return list; //System.out.println("====================================="); /*while (rs.next()) { System.out.println(rs.getString(1) + "," + rs.getString(2)); }*/ //System.out.println("====================================="); } catch (SQLException e) { e.printStackTrace(); } finally { close(stmt); //close(rs); } return null; } // 关闭Statement private void close(Statement stmt) { if (stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } } // 关闭ResultSet private void close(ResultSet rs) { if (rs != null) { try { rs.close(); } catch (SQLException e) { e.printStackTrace(); } } } }