Tutorial | Laur IVAN

Styling HTML to PDF with iText 2.1.7

There are various solutions for producing PDFs from a HTML file, some with excellent results (e.g. ones based on the chrome renderer). Unfortunately, they usually mean adding more dependencies to an existing system. To keep things in check, we’ve chosen to use iText to generate PDFs. Following the previous post, we need to enhance the generated PDF with some styles. Now, the older versions of iText can’t use CSS directly, so we’ll need to produce the styles by hand. iText has a StyleSheet object which can load tag styles via…read more

Jul.07

HTML to PDF with iText 2.1.7

Posted by laur in Software, Tutorial

Sometimes you need to use an older version of a product die to e.g. licensing changes. It’s my case with iText. While the new version looks fantastic, their changes (and removal of e.g. RTF output) are deal breakers for the feature set we need to maintain. Therefore, 2.1.7 is the most recent version we can use. Heh. In maven, this would be:

<dependency>
    <groupId>com.lowagie</groupId>
    <artifactId>itext</artifactId>
    <version>2.1.7</version>
</dependency>

<groupId>com.lowagie</groupId>

<artifactId>itext</artifactId>

</dependency>

The string resulted from the previous article can be printed out fairly easily. First, we create a document and a writer:

// THE PDF
// Doc's begin
final Document document = new Document();
File file = new File("/some/path/out.pdf");
DocWriter docWriter = PdfWriter.getInstance(document, new FileOutputStream(file));

document.open();

// THE PDF

// Doc's begin

final Document document = new Document();

File file = new File("/some/path/out.pdf");

DocWriter docWriter = PdfWriter.getInstance(document, new FileOutputStream(file));

document.open();

We write the document:

HTMLWorker worker = new HTMLWorker(document);
worker.parse(new StringReader(output));

1 2	HTMLWorker worker = new HTMLWorker(document); worker.parse(new StringReader(output));

Jul.07

Load Templates with Pebble

Posted by laur in Software, Tutorial

Pebble is a templating engine. It looks particularly familiar to me because I have been using Django. You have access to blocks, include/import features, loops etc. This post is a simple exercise in loading some templates. Prerequisites I’ve been using Eclipse IDE, but you can use whatever you prefer. I’ve created a maven project and added pebble dependency:

<dependency>
<groupId>com.mitchellbosecke</groupId>
<artifactId>pebble</artifactId>
<version>2.1.0</version>
</dependency>

<groupId>com.mitchellbosecke</groupId>

<artifactId>pebble</artifactId>

</dependency>

The templates I’ve created 3 templates in the resources folder of the project: index.html

<!-- index.html -->
<html>
<head>
</head>
<h1>{{websiteTitle}}</h1>
<p>{{content}}</p>

{% for entry in 1..5 %}
    {{ entry }}
{% endfor %}

<br />
<p>IT WORKS!</p>

<table style="width: 100%">
    <tr>
    {% for entry in 1..5 %}
      {% include "cell" with {"item":entry} %}
    {% endfor %}
    </tr>
</table>

<ul>
{% for entry in 1..5 %}
    {% include "inner" with {"item":entry} %}
{% endfor %}
</ul>
<br />

</html>

<html>

<head>

</head>

<h1>{{websiteTitle}}</h1>

<p>{{content}}</p>

{% for entry in 1..5 %}

{% endfor %}

<br />

<p>IT WORKS!</p>

<tr>

{% for entry in 1..5 %}

{% include "cell" with {"item":entry} %}

{% endfor %}

</tr>

</table>

<ul>

{% for entry in 1..5 %}

{% include "inner" with {"item":entry} %}

{% endfor %}

</ul>

<br />

</html>

cell.html

<td style="text-align: center;">{{item}}</td>

1	<td style="text-align: center;">{{item}}</td>

Note how the {{item}} parameter is taken from the loop in *index.html. inner.html

<li style="color:blue">{{item}}</li>

1	<li style="color:blue">{{item}}</li>

Jun.30

Display a Function’s Errors in Oracle

Posted by laur in Software, Tutorial

TL;DR: Use the power of DBMS_OUTPUT.PUT_LINE, Luke! I’ve built a function along the lines of:

CREATE OR REPLACE FUNCTION HAS_PANEL_FLAG_OK(
  P_USER_ID    in USERS.USER_ID%TYPE,
  P_PANEL_ID   in PANELS.PANEL_ID%TYPE,
)
RETURN integer
IS
  lv_count NUMBER;
BEGIN
  SELECT count(*) into lv_count 
    FROM USERS
    WHERE USERS.PANEL_ID = P_PANEL_ID and USERS.USER_ID = P_USER_ID;
  return lv_count;
EXCEPTION
 when OTHERS then
    return 0;
END;

CREATE OR REPLACE FUNCTION HAS_PANEL_FLAG_OK(

P_USER_ID in USERS.USER_ID%TYPE,

P_PANEL_ID in PANELS.PANEL_ID%TYPE,

)

RETURN integer

lv_count NUMBER;

BEGIN

SELECT count(*) into lv_count

FROM USERS

WHERE USERS.PANEL_ID = P_PANEL_ID and USERS.USER_ID = P_USER_ID;

return lv_count;

EXCEPTION

when OTHERS then

return 0;

END;

When using the function, I got some 0 results and I wanted to know why. The solution I got was using DBMS_OUTPUT.PUT_LINE:

CREATE OR REPLACE FUNCTION HAS_PANEL_FLAG_OK(
  P_USER_ID    in USERS.USER_ID%TYPE,
  P_PANEL_ID   in PANELS.PANEL_ID%TYPE,
)
RETURN integer
IS
  lv_count NUMBER;

  -- Error variables
  v_code  NUMBER;
  v_errm  VARCHAR2(64);
BEGIN
  -- The normal function code
EXCEPTION
 when OTHERS then
    v_code := SQLCODE;
    v_errm := SUBSTR(SQLERRM, 1, 64);
    DBMS_OUTPUT.PUT_LINE (v_code || ' ' || v_errm || '(U: ' || P_USER_ID || ', P:' || P_PANEL_ID || ')');
    return 0;
end;

CREATE OR REPLACE FUNCTION HAS_PANEL_FLAG_OK(

P_USER_ID in USERS.USER_ID%TYPE,

P_PANEL_ID in PANELS.PANEL_ID%TYPE,

)

RETURN integer

lv_count NUMBER;

-- Error variables

v_code NUMBER;

v_errm VARCHAR2(64);

BEGIN

-- The normal function code

EXCEPTION

when OTHERS then

v_code := SQLCODE;

v_errm := SUBSTR(SQLERRM, 1, 64);

DBMS_OUTPUT.PUT_LINE (v_code || ' ' || v_errm || '(U: ' || P_USER_ID || ', P:' || P_PANEL_ID || ')');

return 0;

end;

Now, all you have to do is enable DBMS_OUTPUT in your environment and you’ll see the exceptions. NOTE: This is useful while building and tuning the function. IMHO one should disable the PUT_LINE statements in production. HTH, A little experiment: If you find this post and ad below useful, please check…read more

Jun.29

Call an Oracle Function from Spring with CallableStatement

Posted by laur in Software, Tutorial

Following the previous post, I wondered if there’s a more elegant way to call a function. It turns out there is and it’s based on CallableStatement:

int value = jdbcOperations.execute(
  new CallableStatementCreator() {
    // ...
  },
  new CallableStatementCallback<Integer>() {
    // ...
  }
);

int value = jdbcOperations.execute(

new CallableStatementCreator() {

// ...

new CallableStatementCallback<Integer>() {

// ...

}

);

The CallableStatementCreator sets up the statement and the CallableStatementCallback executes the statement and returns the value up to the execute() call. Having a function:

CREATE OR REPLACE FUNCTION HAS_PANEL_FLAG_OK(
  P_USER_ID    in USERS.USER_ID%TYPE,
  P_PANEL_ID   in PANELS.PANEL_ID%TYPE,
)
RETURN integer
IS
  lv_count NUMBER;
BEGIN
  SELECT count(*) into lv_count 
    FROM USERS
    WHERE USERS.PANEL_ID = P_PANEL_ID and USERS.USER_ID = P_USER_ID;
  return lv_count;
EXCEPTION
 when OTHERS then
    return 0;
END;

CREATE OR REPLACE FUNCTION HAS_PANEL_FLAG_OK(

P_USER_ID in USERS.USER_ID%TYPE,

P_PANEL_ID in PANELS.PANEL_ID%TYPE,

)

RETURN integer

lv_count NUMBER;

BEGIN

SELECT count(*) into lv_count

FROM USERS

WHERE USERS.PANEL_ID = P_PANEL_ID and USERS.USER_ID = P_USER_ID;

return lv_count;

EXCEPTION

when OTHERS then

return 0;

END;

We can build a query string like:

static final String PANEL_OPERATIONS_OK = 
  "{ ? = call HAS_PANEL_FLAG_OK(?, ?) }";

1 2	static final String PANEL_OPERATIONS_OK = "{ ? = call HAS_PANEL_FLAG_OK(?, ?) }";

The CallableStatementCreator instance is then:

CallableStatementCreator statementCreator =
    new CallableStatementCreator() {
  @Override
  public CallableStatement createCallableStatement(Connection con) throws SQLException {
    CallableStatement cs = con.prepareCall(PANEL_OPERATIONS_OK);
    cs.registerOutParameter(1, Types.INTEGER); // The returned result
    cs.setString(2, userId);
    cs.setString(3, panelId);
    return cs;
  }
}

CallableStatementCreator statementCreator =

new CallableStatementCreator() {

@Override

public CallableStatement createCallableStatement(Connection con) throws SQLException {

CallableStatement cs = con.prepareCall(PANEL_OPERATIONS_OK);

cs.registerOutParameter(1, Types.INTEGER); // The returned result

cs.setString(2, userId);

cs.setString(3, panelId);

return cs;

}

This states the first parameter is a result, the second and 3rd parameter are function parameters. NOTE: Be careful because you can specify indices…read more

Jun.29

Call an Oracle Function from Spring

Posted by laur in Software, Tutorial

The easiest way to call a function from Spring is using SELECT. For example, having a function HAS_PANEL_FLAG_OK with two parameters and returning an integer, the function call looks like:

select  panel_id, 
  HAS_PANEL_FLAG_OK('17584', panel_id) AS flag
  FROM panels
  WHERE panel_id LIKE '%30'
 ;

select panel_id,

HAS_PANEL_FLAG_OK('17584', panel_id) AS flag

FROM panels

WHERE panel_id LIKE '%30'

;

This will return all flags for the panels matching the condition. Java Call The query string can be something like:

static final String STATEMENT = "select  panel_id, " +
  "HAS_PANEL_FLAG_OK('17584', panel_id) AS flag " +
  "FROM panels" +
  "WHERE panel_id LIKE ?"

static final String STATEMENT = "select panel_id, " +

"HAS_PANEL_FLAG_OK('17584', panel_id) AS flag " +

"FROM panels" +

"WHERE panel_id LIKE ?"

and the actual query will be:

jdbcOperations.queryForInt(SELECT_PANEL_IS_LOCKED, new Object[] {
    "%30"
});

jdbcOperations.queryForInt(SELECT_PANEL_IS_LOCKED, new Object[] {

"%30"

});

The problem I’ve encountered is the ability to specify an argument which is not part of the query. Something like this:

static final String STATEMENT = "select  panel_id, " +
  "HAS_PANEL_FLAG_OK(?, panel_id) AS flag " + // the first function parameter is parametereised
  "FROM panels" +
  "WHERE panel_id LIKE ?"

jdbcOperations.queryForInt(SELECT_PANEL_IS_LOCKED, new Object[] {
    "17584",
    "%30"
});

static final String STATEMENT = "select panel_id, " +

"HAS_PANEL_FLAG_OK(?, panel_id) AS flag " + // the first function parameter is parametereised

"FROM panels" +

"WHERE panel_id LIKE ?"

jdbcOperations.queryForInt(SELECT_PANEL_IS_LOCKED, new Object[] {

"17584",

"%30"

});

I’ll investigate this later… HTH, A little experiment: If…read more

Jun.28

Easy Volumio Plugin Development

Posted by laur in Software, Tutorial, Uncategorized

The past few days I’ve been struggling with building a volume controller plugin for volumio. My initial routine would be something like: edit the source code on a PC zip the code and some node_modules bundled from another plugin load the plugin in volumio This presents several issues: Slow deployment cycle (even if partially automated) Unable to restart volumio without rebooting New way I’ve been looking for more info and I’ve devised a new process: Create the plugin on the raspberry pi You need to download all the prerequisites (e.g….read more

Jun.23

SoundMachine Build Log 02

Posted by laur in Hardware, Tutorial

I’ve decided to put in a knob to control the volume directly on the box itself. It will be controlled by volumio itself via a plugin, much like the GPIO Buttons plugin. Since this is really a development kit approach, the hardware consists of: A KY-040 rotary encoder and A screw-based prototype board Both are relatively easy and cheap to find and buy. Rotary encoder The encoder is straight-forward cheap version, with a push button too, just in case. It’s even mounted on a PCB and has pins too, so…read more

Jun.15

SoundMachine
Build Log 01

Posted by laur in Hardware, Tutorial

A while ago I’ve decided to try my hand at replacing my Sonos system with a DIY version of a sound system. I have two reasons to do this: I think it’s going to be fun and I have a bunch of FLAC files at odd resolutions which are not really playable by the Sonos system. After giving it some thought, I’ve settled on the following configuration: A Raspberry Pi A sound card for the Raspberry Pi. For starters I’ll be going with a Chinese clone An amplifier A couple…read more

Jun.13

HifiBerry Pin Usage

Posted by laur in Hardware, Tutorial

The past few days I’ve been struggling with the unknown of how many pins from the GPIO interface are actually used by the HifiBerry sound card (or my clone). Fortunately, I’ve found the used pins: As you can see, there are quite a few pins left for other things, which means I won’t have to use an arduino to control things anymore :) HTH, A little experiment: If you find this post and ad below useful, please check the ad out :-)