JDBC的流数据
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。
用于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,然后XML_Data.xml將被上傳到該表中。
將下面的示例拷貝并粘帖到JDBCExample.java中,編譯并運行它,如下所示:
//Import required packages import java.sql.*; import java.io.*; import java.util.*;public class JDBCExample {// JDBC driver name and database URLstatic final String JDBC_DRIVER = "com.mysql.jdbc.Driver";static final String DB_URL = "jdbc:mysql://localhost/Test?serverTimezone=UTC";// Database credentialsstatic 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 driverClass.forName("com.mysql.jdbc.Driver");// Open a connectionSystem.out.println("Connecting to database...");conn = DriverManager.getConnection(DB_URL, USER, PASS);// Create a Statement object and build tablestmt = conn.createStatement();createXMLTable(stmt);// Open a FileInputStreamFile f = new File("XML_Data.xml");long fileLength = f.length();FileInputStream fis = new FileInputStream(f);// Create PreparedStatement and stream dataString 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 rowSQL = "SELECT Data FROM XML_Data WHERE id=100";rs = stmt.executeQuery(SQL);// Get the first rowif (rs.next()) {// Retrieve data from input streamInputStream 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 resourcestry {if (stmt != null)stmt.close();} catch (SQLException se2) {} // nothing we can dotry {if (pstmt != null)pstmt.close();} catch (SQLException se2) {} // nothing we can dotry {if (conn != null)conn.close();} catch (SQLException se) {se.printStackTrace();} // end finally try} // end trySystem.out.println("Goodbye!");}// end mainpublic static void createXMLTable(Statement stmt) throws SQLException {System.out.println("Creating XML_Data table...");// Create SQL StatementString 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
==>如有問題,請聯系我:easonjim#163.com,或者下方發表評論。<==總結
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