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JDBC的流數據

employee example 存儲 while integer update ins state into

以下內容引用自http://wiki.jikexueyuan.com/project/jdbc/streaming-data.html:

PreparedStatement對象必須具備使用輸入和輸出流來提供參數數據的能力。這能夠將整個文件存儲到數據庫列中,這樣數據庫就能存儲大型數據,例如CLOB和BLOB數據類型。

用於流數據有下列幾種方法:

  • setAsciiStream():該方法是用來提供較大的ASCII值。
  • setCharacterStream():該方法是用來提供較大的UNICODE值。
  • setBinaryStream():該方法是用來提供較大的二進制值。

setXXXStream()方法需要一個額外的參數,該參數是除了參數占位符的文件大小。這個參數通知驅動程序通過使用流有多少數據被發送到數據庫中。

示例:

假要上傳一個名為XML_Data.xml的XML文件到數據庫的表中。下面是該XML文件的內容:

<?xml version="1.0"?>
<Employee>
<id>100</id>
<first>Zara</first>
<last>Ali</last>
<Salary>10000</Salary>
<Dob>18-08-1978</Dob>
<Employee>

將該XML文件和要運行的示例保存在相同的目錄的。

這個示例將創建一個數據庫表XML_Data,然後XML_Data.xml將被上傳到該表中。

將下面的示例拷貝並粘帖到JDBCExample.java中,編譯並運行它,如下所示:

//Import required packages
import java.sql.*;
import java.io.*;
import java.util.*;

public class JDBCExample {
    // JDBC driver name and database URL
    static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    static final String DB_URL = "jdbc:mysql://localhost/Test?serverTimezone=UTC";

    
// Database credentials static final String USER = "root"; static final String PASS = "root"; public static void main(String[] args) { Connection conn = null; PreparedStatement pstmt = null; Statement stmt = null; ResultSet rs = null; try { // Register JDBC driver Class.forName("com.mysql.jdbc.Driver"); // Open a connection System.out.println("Connecting to database..."); conn = DriverManager.getConnection(DB_URL, USER, PASS); // Create a Statement object and build table stmt = conn.createStatement(); createXMLTable(stmt); // Open a FileInputStream File f = new File("XML_Data.xml"); long fileLength = f.length(); FileInputStream fis = new FileInputStream(f); // Create PreparedStatement and stream data String SQL = "INSERT INTO XML_Data VALUES (?,?)"; pstmt = conn.prepareStatement(SQL); pstmt.setInt(1, 100); pstmt.setAsciiStream(2, fis, (int) fileLength); pstmt.execute(); // Close input stream fis.close(); // Do a query to get the row SQL = "SELECT Data FROM XML_Data WHERE id=100"; rs = stmt.executeQuery(SQL); // Get the first row if (rs.next()) { // Retrieve data from input stream InputStream xmlInputStream = rs.getAsciiStream(1); int c; ByteArrayOutputStream bos = new ByteArrayOutputStream(); while ((c = xmlInputStream.read()) != -1) bos.write(c); // Print results System.out.println(bos.toString()); } // Clean-up environment rs.close(); stmt.close(); pstmt.close(); conn.close(); } catch (SQLException se) { // Handle errors for JDBC se.printStackTrace(); } catch (Exception e) { // Handle errors for Class.forName e.printStackTrace(); } finally { // finally block used to close resources try { if (stmt != null) stmt.close(); } catch (SQLException se2) { } // nothing we can do try { if (pstmt != null) pstmt.close(); } catch (SQLException se2) { } // nothing we can do try { if (conn != null) conn.close(); } catch (SQLException se) { se.printStackTrace(); } // end finally try } // end try System.out.println("Goodbye!"); }// end main public static void createXMLTable(Statement stmt) throws SQLException { System.out.println("Creating XML_Data table..."); // Create SQL Statement String streamingDataSql = "CREATE TABLE XML_Data " + "(id INTEGER, Data LONG)"; // Drop table first if it exists. try { stmt.executeUpdate("DROP TABLE XML_Data"); } catch (SQLException se) { } // do nothing // Build table. stmt.executeUpdate(streamingDataSql); }// end createXMLTable }// end JDBCExample

當運行JDBCExample時,它將展示下面的結果:

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測試工程:https://github.com/easonjim/5_java_example/tree/master/jdbcbasics/test9

JDBC的流數據