Printing out results in case of object-relational table (Oracle)

Question

I have made a table with this structure:
CREATE OR REPLACE TYPE Boat AS OBJECT(
Name varchar2(30),
Ident number,
CREATE OR REPLACE TYPE Type_boats AS TABLE OF Boat;
CREATE TABLE HOUSE(
Name varchar2(40),
MB Type_boats)
NESTED TABLE MB store as P_Boat;
INSERT INTO House VALUES ('Name',Type_boats(Boat('Boat1', 1)));
I am using java to print out all the results by calling a procedure.
CREATE OR REPLACE package House_boats
PROCEDURE add(everything works here)
PROCEDURE results_view;
END House_boats;
CREATE OR REPLACE Package.body House_boats AS
PROCEDURE add(everything works here) AS LANGUAGE JAVA
Name House_boats.add(...)
PROCEDURE results_view AS LANGUAGE JAVA
Name House_boats.resuts_view();
END House_boats;
However, I am not able to get Results.view working in case of object-relation table. This is how I do it in the situation of relational table.
CALL House_boats.results_view();
House_boats.java file which is loaded using LOADJAVA:
import java.sql.*;
import java io.*;
public class House_boats {
public static void results_view ()
   throws SQLException
   { String sql =
   "SELECT * from House";
   try { Connection conn = DriverManager.getConnection
("jdbc:default:connection:");
   PreparedStatement pstmt = conn.prepareStatement(sql);
   ResultSet rset = pstmt.executeQuery();
  printResults(rset);
  rset.close();
  pstmt.close();
   catch (SQLException e) {System.err.println(e.getMessage());
static void printResults (ResultSet rset)
   throws SQLException { String buffer = "";
   try { ResultSetMetaData meta = rset.getMetaData();
   int cols = meta.getColumnCount(), rows = 0;
   for (int i = 1; i <= cols; i++)
   int size = meta.getPrecision(i);
   String label = meta.getColumnLabel(i);
   if (label.length() > size) size = label.length();
   while (label.length() < size) label += " ";
  buffer = buffer + label + " "; }
  buffer = buffer + "\n";
   while (rset.next()) {
  rows++;
   for (int i = 1; i <= cols; i++) {
   int size = meta.getPrecision(i);
   String label = meta.getColumnLabel(i);
   String value = rset.getString(i);
   if (label.length() > size) size = label.length();
   while (value.length() < size) value += " ";
  buffer = buffer + value + " ";  }
  buffer = buffer + "\n";   }
   if (rows == 0) buffer = "No data found!\n";
   System.out.println(buffer); }
   catch (SQLException e) {System.err.println(e.getMessage());}  }
How do I print out the results correctly in my case of situation?
Thank you in advance

Answer 1

I have made a table with this structure:
I am using java to print out all the results by calling a procedure.
However, I am not able to get Results.view working in case of object-relation table. This is how I do it in the situation of relational table.
How do I print out the results correctly in my case of situation?
There are several things wrong with your code and methodology
1. The code you posted won't even compile because there are several syntax issues.
2. You are trying to use/test Java in the database BEFORE you get the code working outside the DB
3. Your code is not using collections in JDBC properly
I suggest that you use a different, proven approach to developing Java code for use in the DB
1. Use SIMPLE examples and then build on them. In this case that means don't add collections to the example until ALL other aspects of the app work properly.
2. Create and test the Java code OUTSIDE of the database. It is MUCH easier to work outside the database and there are many more tools to help you (e.g. NetBeans, debuggers, DBMS_OUTPUT windows, etc). Trying to debug Java code after you have already loaded it into the DB is too difficult. I'm not aware of anyone, even at the expert level, that develops that way.
3. When using complex functionality like collections first read the Oracle documentation (JDBC Developer Guide and Java Developer's Guide). Those docs have examples that are known to work.
http://docs.oracle.com/cd/B28359_01/java.111/b31225/chfive.htm
http://docs.oracle.com/cd/E11882_01/java.112/e16548/oraarr.htm#sthref583
The main issue with your example is #3 above; you are not using collections properly:
String value = rset.getString(i);
A collection is NOT a string so why would you expect that to work for a nested table?
A collection needs to be treated like a collection. You can even treat the collection as a separate result set. Create your code outside the database and use the debugger in NetBeans (or other) on this replacement code for your 'printResults' method:
static void printResults (ResultSet rset) throws SQLException {
    try {
       ResultSetMetaData meta = rset.getMetaData();
       while (rset.next()) {
           ResultSet rs = rset.getArray(2).getResultSet();
           rs.next();
           String ndx = rs.getString(1);
           Struct struct = (Struct) rs.getObject(2);
           System.out.println(struct.getSQLTypeName());
           Object [] oa = struct.getAttributes();
           for (int j = 0; j < oa.length; j++) {
              System.out.println(oa[j]);
    } catch  (SQLException e) {
       System.err.println(e.getMessage());
That code ONLY deals with column 2 which is the nested table. It gets that collection as a new resultset ('rs'). Then it gets the contents of that nested table as an array of objects and prints out the attributes of those objects so you can see them.
Step through the above code in a debugger so you can SEE what is happening. NetBeans also lets you enter expressions such as 'rs' in an evaluation window so you can dynamically try the different methods to see what they do for you.
Until you get you code working outside the database don't even bother trying to load it into the DB and create a Java stored procedure.
Since your current issue has nothing to do with this forum I suggest that you mark this thread ANSWERED and repost it in the JDBC forum if you need further help with this issue.
https://forums.oracle.com/community/developer/english/java/database_connectivity
When you repost you can include a link to this current thread if you want. Once your Java code is actually working then try the Java Stored procedure examples in the Java Developer's Guide doc linked above.
At the point you have any issues that relate to Java stored procedures then you should post them in the SQL and PL/SQL forum
https://forums.oracle.com/community/developer/english/oracle_database/sql_and_pl_sql