Exception in thread "main" java.lang.Error: unsolved compilation problems:

Question

Hi everyone, I have some kind of problem in my jdbc code. I am trying to connect via mysql, but it will provide error.my error log below, if you have time, please help me.

Exception in thread "main" java.lang.Error: Unresolved compilation problems: BLOB cannot be resolved to a type BLOB cannot be resolved to a type at serialize.SerializeDeserialze.main(SerializeDeserialze.java:73) 

my code is below. I am using the mysql-connector-java-5.1.20.jar driver

 package serialize; /* By vivek */ import java.io.InputStream; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.OutputStream; import java.sql.CallableStatement; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.ArrayList; import java.util.List; import oracle.sql.BLOB; /**** CREATE TABLE java_objects (object_id NUMBER, object_name varchar(128), object_value BLOB DEFAULT empty_blob(), primary key (object_id)); SQL> desc java_objects; Name Null? Type ----------------------------------------- -------- ---------------------------- OBJECT_ID NOT NULL NUMBER OBJECT_NAME VARCHAR2(128) OBJECT_VALUE BLOB SQL> select SEQUENCE_NAME, MIN_VALUE, MAX_VALUE, INCREMENT_BY, LAST_NUMBER from user_sequences; SEQUENCE_NAME MIN_VALUE MAX_VALUE INCREMENT_BY LAST_NUMBER ------------------------------ ---------- ---------- ------------ ----------- ID_SEQ 1 1.0000E+27 1 21 JAVA_OBJECT_SEQUENCE 1 1.0000E+27 1 1 */ public class SerializeDeserialze { public static void main(String[] args) throws Exception { String WRITE_OBJECT_SQL = "BEGIN " + " INSERT INTO java_objects(object_id, object_name, object_value) " + " VALUES (?, ?, empty_blob()) " + " RETURN object_value INTO ?; " + "END;"; String READ_OBJECT_SQL = "SELECT object_value FROM java_objects WHERE object_id = ?"; Connection conn = getOracleConnection(); conn.setAutoCommit(false); List<Object> list = new ArrayList<Object>(); list.add("This is a short string."); list.add(new Integer(1234)); list.add(new java.util.Date()); // write object to Oracle long id = 0001; String className = list.getClass().getName(); CallableStatement cstmt = conn.prepareCall(WRITE_OBJECT_SQL); cstmt.setLong(1, id); cstmt.setString(2, className); cstmt.registerOutParameter(3, java.sql.Types.BLOB); cstmt.executeUpdate(); BLOB blob = (BLOB) cstmt.getBlob(3); OutputStream os = blob.getBinaryOutputStream(); ObjectOutputStream oop = new ObjectOutputStream(os); oop.writeObject(list); oop.flush(); oop.close(); os.close(); // Read object from oracle PreparedStatement pstmt = conn.prepareStatement(READ_OBJECT_SQL); pstmt.setLong(1, id); ResultSet rs = pstmt.executeQuery(); rs.next(); InputStream is = rs.getBlob(1).getBinaryStream(); ObjectInputStream oip = new ObjectInputStream(is); Object object = oip.readObject(); className = object.getClass().getName(); oip.close(); is.close(); rs.close(); pstmt.close(); conn.commit(); // de-serialize list a java object from a given objectID List listFromDatabase = (List) object; System.out.println("[After De-Serialization] list=" + listFromDatabase); conn.close(); } private static Connection getHSQLConnection() throws Exception { Class.forName("org.hsqldb.jdbcDriver"); System.out.println("Driver Loaded."); String url = "jdbc:hsqldb:data/tutorial"; return DriverManager.getConnection(url, "sa", ""); } public static Connection getMySqlConnection() throws Exception { String driver = "org.gjt.mm.mysql.Driver"; String url = "jdbc:mysql://localhost/demo2s"; String username = "oost"; String password = "oost"; Class.forName(driver); Connection conn = DriverManager.getConnection(url, username, password); return conn; } public static Connection getOracleConnection() throws Exception { String driver = "oracle.jdbc.driver.OracleDriver"; String url = "jdbc:oracle:thin:@localhost:1521:databaseName"; String username = "userName"; String password = "password"; Class.forName(driver); // load Oracle driver Connection conn = DriverManager.getConnection(url, username, password); return conn; } 

Answer 1

This error occurs when you use Eclipse as an IDE and try to run code that does not even compile. Check the problem presentation in Eclipse and fix compilation errors before running the application.

Answer 2

You are using the MySQL driver, but your class uses the Oracle BLOB class. Either use the Oracle JDBC driver, or use a different class for the BLOB.

Since your code mentions HSQL, MySQL, and Oracle, you probably want to get rid of the Oracle-specific BLOB implementation.