JDBC读取SciDB数据

爱被打了一巴掌 2022-07-16 04:10 190阅读 0赞

SciDB一个典型的Array Database，官网地址：[http://www.paradigm4.com/][http_www.paradigm4.com]，提供了C++，Java，Python和R的接口。

下面说说如何使用Java的接口（JDBC）读取SciDB数据：  
我使用的SciDB版本是14.12，JDK版本为1.7。  
依赖的JDBC的jar包可从[https://downloads.paradigm4.com/client/14.12/jdbc/][https_downloads.paradigm4.com_client_14.12_jdbc]下载，主要用到的jar包括scidb4j.jar和iquery.jar。  
此外，还需要Google的protolib库，版本为2.4.1。

代码如下：

package cn.tzy.scidb;
    
    import org.scidb.jdbc.IResultSetWrapper;
    
    import java.sql.*;
    
    public class Main {
    
        public static void main(String[] args) {
            try {
                Class.forName("org.scidb.jdbc.Driver");
            } catch (ClassNotFoundException ex) {
                System.out.println("Driver is not in the CLASSPATH -> " + ex);
            }
    
            String iqueryHost = "127.0.0.1";
            String iqueryPort = "1239";
            String arrayName = "landsat_wuhan";
    
            try {
                String url = "jdbc:scidb://" + iqueryHost + ":" + iqueryPort + "/";
                Connection conn = DriverManager.getConnection(url);
                ResultSet res;
                try (Statement st = conn.createStatement()) {
                    res = st.executeQuery("select * from " + arrayName);
                }
                ResultSetMetaData meta = res.getMetaData();
                System.out.println("Source array name: " + meta.getTableName(0));
                System.out.println(meta.getColumnCount() + " columns:");
                IResultSetWrapper resWrapper = res.unwrap(IResultSetWrapper.class);
    
                // 输出Array的元数据
                for(int i = 1; i <= meta.getColumnCount(); ++i) { 
                    System.out.println(meta.getColumnName(i) + " - " + meta.getColumnTypeName(i) + " - is attribute:" + resWrapper.isColumnAttribute(i));
                }
    
                int count = 0;
                // 输出Array的前10行数据
                while(!res.isAfterLast() && count < 10) {
                    System.out.println(res.getLong(1) + " " + res.getLong(2) + " " + res.getShort(3));
                    res.next();
                    count++;
                }
            } catch (SQLException ex) {
                System.out.println(ex);
            }
        }
    }

输出结果如下：

Source array name: landsat_wuhan@1
    3 columns:
    y - int64 - is attribute:false
    x - int64 - is attribute:false
    band1 - uint8 - is attribute:true
    0 0 0
    0 1 0
    0 2 0
    0 3 0
    0 4 0
    0 5 0
    0 6 0
    0 7 0
    0 8 0
    0 9 0

[http_www.paradigm4.com]: http://www.paradigm4.com/
[https_downloads.paradigm4.com_client_14.12_jdbc]: https://downloads.paradigm4.com/client/14.12/jdbc/