Author Archive

Preparation to SCEA 5 Part II Notes

Wednesday, December 8th, 2010

Some notes and links that I found useful preparing for SCEA http://docs.sun.com/app/docs/doc/819-2326/gaxqg?a=view

Spring reference documentation

Tuesday, October 19th, 2010

In a recent project I had to remember Spring MVC, so I found the reference documentation from spring and thought it’s a good thing to post: http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/pdf/spring-framework-reference.pdf.

For spring MVC 3.0 controllers try the following url http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/mvc.html

How to process queries that have lists/ arrays as parameters

Tuesday, October 12th, 2010

There were multiple times in recent projects where I had to write SQL for queries that had lists or arrays as parameters. There are a few ways of dealing with this issue, since API do not allow this natively.

One way is to use temporary table, insert all the ids in it and then join to that table in the query. Sybase has ‘native’ support for such temp tables, as long as you are using the same connection to insert the ids, and then execute the query.
To get the single connection out of the pool,use the following code:
JdbcTemplate scdsJdbcTemplate = null;
final String tempTableName = “#assets”;
try {
scds = new SingleConnectionDataSource(getJdbcTemplate().getDataSource().getConnection(), true);
scdsJdbcTemplate = new JdbcTemplate(scds);

createTempTableForIds(ids, tempTableName, scdsJdbcTemplate);

To insert ids into temp table and drop it after it was used, use the following code:
protected void createTempTableForIds(final List<String> ids, String tempTableName, JdbcTemplate jdbcTemplate) throws SQLException {
if (!tempTableName.startsWith(“#”)) {
throw new RuntimeException(“Temp table ” + tempTableName + ” does not start with #, which is a” +
“requirement for a temp table”);
}

final String TABLE_CREATE = “create table #_TABLE_NAME_ (barraId varchar(32))”;
final String TABLE_POPULATE = “insert into #_TABLE_NAME_ (barraId) values(?)”;

jdbcTemplate.execute(“sp_dboption asgp_db, ‘ddl in tran’, true”);
jdbcTemplate.execute(TEMP_TABLE_CREATE.replaceFirst(“#_TABLE_NAME_”, tempTableName));

String insertSql = TABLE_POPULATE.replaceFirst(“#_TABLE_NAME_”, tempTableName);

doInsertValuesIntoTempable(ids, jdbcTemplate, insertSql);
}

protected void doInsertValuesIntoTempable(final List<String> ids, JdbcTemplate jdbcTemplate, String insertSql) throws SQLException {
BatchPreparedStatementSetter batchObject = new BatchPreparedStatementSetter() {
public void setValues(PreparedStatement ps, int i) throws SQLException {
ps.setString(1, ids.get(i));
}

public int getBatchSize() {
return ids.size();
}
};

int[] updateCounts = jdbcTemplate.batchUpdate(insertSql, batchObject);

/* sanity checking results */
if (updateCounts.length != barraIdAssets.size()) {
throw new SQLException(“Not all Ids were inserted # of inserts ” +
updateCounts.length + ” vs. # of Ids needed to be inserted ” + barraIdAssets.size());
}
for(int i=0; i< updateCounts.length; ++i) {
if (updateCounts[i] != 1) {
throw new SQLException(“Could not insert id” + ids.get(i)
+ ” inserted ” + updateCounts[i] + ” instead of 1 row”);
}
}
}

public static void dropTempTable(String tempTableName, JdbcTemplate jdbcTemplate) {
if (!tempTableName.startsWith(“#”)) {
throw new RuntimeException(“Temp table ” + tempTableName + ” does not start with #, which is a” +
“requirement for a temp table”);
}
String TABLE_DROP = “drop table #_TABLE_NAME_ “;
jdbcTemplate.execute(TABLE_DROP.replaceFirst(“#_TABLE_NAME_”, tempTableName));
}

The second way, you can dynamically create an in-clause and populate it with the ids, where you will have to make sure to batch #, e.g. possibly create a few queries since each one would work on subset of ids. You might be able then fire these queries in parallel and get the results that way.

Passed Java Certified Architect Exam part I

Friday, June 25th, 2010

I passed Java Certified Architect Exam part I – here are my preparation notes.

How to Host a Web Server at Home With Dynamic DNS

Friday, June 6th, 2008

A good article by¬† Jeff Black oh how to host a web server at home could be found at http://codebeneath.blogspot.com/2007/08/how-to-host-web-server-at-home-with.html In my case, I’ m trying to find a good service that would host my web-apps and would not be too expensive – so I might try his approach.