Java - Exception in thread "main" java.lang.Error: Unresolved compilation problems
82,563
Solution 1
This error happens when you use Eclipse as IDE and try to run code that doesn't even compile. Check your Problems view in Eclipse, and fix the compilation errors before executing the application.
Solution 2
You are using a MySQL driver, but your class uses an Oracle BLOB class. Either use the Oracle JDBC driver, or use a different class for BLOB.
Since your code mentions HSQL, MySQL and Oracle, you will probably want to get rid of the Oracle-specific BLOB implementation.
Author by
vivek rai
Updated on July 09, 2022Comments
-
vivek rai almost 2 years
I have some problem in my JDBC code. I am trying to connect through MySQL but it gives me an error. My error log is given below if you have some time.
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 given below. I am using
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; }
-
Nick Constantine over 5 yearsThanks, this was it. This happened to me when I added an import statement before the package statement.