info.michael-simons.eu

Modify memory settings of the Oracle Aurora JVM

Use the following class to view and modify the settings of the embedded JVM inside an Oracle database. The class has been tested on 10g and 11g, memory settings and information are in Megabyte.

SET DEFINE OFF
CREATE OR REPLACE AND COMPILE JAVA SOURCE NAMED "MemoryStatistics" AS
import oracle.aurora.vm.OracleRuntime;

public class MemoryStatistics {
    public final static int MB_MULTIPLICATOR = 1024*1024;

	public static String getStatistics() {
		final Runtime runtime = Runtime.getRuntime();
		
		final long totalMemory = runtime.totalMemory();
		final long maxMemory = runtime.maxMemory();
		final long usedMemory = totalMemory - runtime.freeMemory();

        return new StringBuffer()
        	.append(usedMemory/MB_MULTIPLICATOR)
        	.append(" / ")
        	.append(totalMemory/MB_MULTIPLICATOR)
        	.append(" MB (used / total), Maximum ")
        	.append(OracleRuntime.getMaxMemorySize()/MB_MULTIPLICATOR)
        	.append(", running on ")
        	.append(System.getProperty("java.version"))
        	.toString();
	}
    
    public static long getMaxMemorySize() {
        return OracleRuntime.getMaxMemorySize() / MB_MULTIPLICATOR;
    }
    
    public static void setMaxMemorySize(final long maxMemorySize) {
        OracleRuntime.setMaxMemorySize(maxMemorySize*MB_MULTIPLICATOR);
    }
}
/

SHO ERR;

CREATE OR REPLACE PROCEDURE p_set_max_memory_size(p_max_memory_size IN NUMBER) IS LANGUAGE JAVA
    NAME 'MemoryStatistics.setMaxMemorySize(long)';
/
 
CREATE OR REPLACE FUNCTION f_get_max_memory_size RETURN NUMBER IS LANGUAGE JAVA
    NAME 'MemoryStatistics.getMaxMemorySize() return java.lang.Long';
/
 
CREATE OR REPLACE FUNCTION f_get_memory_statistics RETURN VARCHAR2 IS LANGUAGE JAVA
    NAME 'MemoryStatistics.getStatistics() return java.lang.String';
/
 
SELECT f_get_max_memory_size() FROM dual;
 
SELECT f_get_memory_statistics() FROM dual;
 
BEGIN
    p_set_max_memory_size(512);
END;
/
 
SELECT f_get_memory_statistics() FROM dual;

The memory settings is persistent across sessions, at least with my current setup.

Filed in Java, Oracle | Comments (0) »

CSRF protection with Spring Security revisited

At the end of last year, Spring Security 3.2 was released and brought a lot of new features, among them a built-in “Cross Site Request Forgery” protection”.

Nearly two years earlier i wrote my CSRF protection implementation with Spring Security 3.1, have a look here.

I really like the built-in implementation and most of it is very similar to my solution. The main difference is that the protection is at security filter level and not at application level like mine was. Also they use a token class for encapsulating the tokens name and value.

My solution can be very easily adapted to Spring Security 3.2.

First of all, configure it with the onliner

<csrf  />

or use the new annotation based configuration method.

Then throw away everything from my solution except the CSRFTokenTag. Edit the later one to contain the following code:

import java.io.IOException;
import java.util.Random;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
 
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Configurable;
import org.springframework.security.web.csrf.CsrfToken;
import org.springframework.security.web.csrf.CsrfTokenRepository;
 
/**
 * Creates a hidden input field with the CSRF Token
 * @author michael.simons, 2011-09-20
 */
@Configurable
public class CSRFTokenTag extends TagSupport {
	private final static Random random = new Random(System.currentTimeMillis());
 
	private static final long serialVersionUID = 745177955805541350L;
 
	private boolean plainToken = false;
	private String elementId;
 
	@Autowired
	private CsrfTokenRepository csrfTokenRepository;
 
	@Override
	public int doStartTag() throws JspException {		
		final CsrfToken token = csrfTokenRepository.loadToken((HttpServletRequest) super.pageContext.getRequest());
		if(token != null)
			try {
				if(plainToken)
					pageContext.getOut().write(token.getToken());
				else
					pageContext.getOut().write(String.format("<input type=\"hidden\" name=\"%s\" id=\"%s\" value=\"%s\" />", token.getParameterName(), StringUtils.isNotBlank(this.elementId) ? this.elementId : String.format("%s_%d", token.getParameterName(), random.nextInt()), token.getToken()));
			} catch (IOException e) {
			}
		return SKIP_BODY;
	}
 
	@Override
	public int doEndTag() throws JspException {
		return EVAL_PAGE;
	}
 
	public boolean isPlainToken() {
		return plainToken;
	}
 
	public void setPlainToken(boolean plainToken) {
		this.plainToken = plainToken;
	}
 
	public String getElementId() {
		return elementId;
	}
 
	public void setElementId(String elementId) {
		this.elementId = elementId;
	}	
}

The guys at Spring have a nice suggestions for including the token for AJAX/Jsons request. The new filter also validates request headers. The recommend adding the header name and token value to the pages meta information like so

  <meta name="_csrf" content="${_csrf.token}"/>
  <meta name="_csrf_header" content="${_csrf.headerName}"/>

and then manually add the header to each JavaScript request made with jQuery.

An alternative for jQuery users would be the following pre filter:

$.ajaxPrefilter(function(options, originalOptions, jqXHR) {
	var token = $("meta[name='_csrf']").attr("content");
	var header = $("meta[name='_csrf_header']").attr("content");		  
	jqXHR.setRequestHeader(header, token);
});

I’m happy to be able to get rid of some code of mine, though the solution worked quite well for 2 years now.

Filed in English posts, Java | Comments (1) »

1433 commits or: gitshots 2013

While my project is full of pictures, this blog lacks some images and stuff…

So for the last post in 2013 and the last commit being from the night before, i’ll add some fun content, a time-lapse of 1433 gitshots since July, 21st. Gitshot? What the heck is a git shot?

This post-commit hook:

#!/usr/bin/env ruby
file="~/.gitshots/#{Time.now.to_i}.jpg"
unless File.directory?(File.expand_path("../../rebase-merge", __FILE__))
  system "/opt/local/bin/imagesnap -q -w 1 #{file} &"
end
exit 0

Everytime i make a commit, the webcam takes a picture using and puts it in ~/.gitshots. The whole idea was inspired by Víctors .

This is how it looks:

[jwplayer file=”http://info.michael-simons.eu/wp-content/uploads/2013/12/gitshots2013.mp4″ width=”480″]

I must say i was shocked… I look horrible while coding. Sorry, dear colleagues, there’s nothing to be afraid of. Most of the time.

Having said that, all the best for 2014. Enjoy coding and life.

Filed in English posts, Spaß | Comments (0) »

SQL Snippets

Some useful SQL Snippets:

Oracle

Create a date without any formatting hassle (like to_date):

SELECT DATE'2014-01-01' FROM dual;

Extract values as numbers from a date object

SELECT EXTRACT (YEAR FROM DATE'2013-05-06') FROM dual;
SELECT EXTRACT (MONTH FROM DATE'2013-05-06') FROM dual;
SELECT EXTRACT (DAY FROM DATE'2013-05-06') FROM dual;

Conversion of geographical coordinates into different coordinate systems:

SELECT srid,cs_name FROM cs_srs WHERE srid IN (82027, 82032, 8307)
 
-- Von GK4 nach GK3
SELECT sdo_cs.transform(
  SDO_GEOMETRY(2001, 82032, SDO_POINT_TYPE(4465656.81, 5338112.31, NULL), NULL, NULL ), -- Geometry in GK4
  82027                                                                                 -- Zielkoordinatensystem
) FROM dual;
 
-- und zurück
SELECT sdo_cs.transform(
  SDO_GEOMETRY(2001, 82027, SDO_POINT_TYPE(3688714.69, 5341125.2, NULL), NULL, NULL ), -- Geometry in GK3
  82032                                                                                -- Zielkoordinatensystem
) FROM dual;
 
-- und wenn wir schon dabei sind nach WSG84 (google)
SELECT sdo_cs.transform(
  SDO_GEOMETRY(2001, 82027, SDO_POINT_TYPE(3688714.69, 5341125.2, NULL), NULL, NULL ), -- Geometry in GK3
  8307                                                                                -- Zielkoordinatensystem
) FROM dual;

Select the tables that have a foreign key on a given table:

SELECT r.table_name, r.constraint_name
FROM all_constraints s
JOIN all_constraints r ON r.constraint_type = 'R' AND r.r_constraint_name = s.constraint_name
WHERE LOWER(s.table_name) = '<table_name>';

Last update: 2014/01/17

See also:

Git Snippets and Maven Snippets.

Filed in English posts | Comments (0) »

Archiving OS X Mavericks tags (and other data) with git

For the last 6 months i’ve been archiving all my paper work (OCR’ing and than trashing it) to a personal documents repository.

There are some document managers out there but every single one felt like overkill to me, so i just stick to a pretty simple directory structure which is enough for me.

Although i need those documents across devices, i didn’t want to use a cloud service to sync them. git does a pretty good job here.

With Mac OS X Mavericks comes a great new feature: Tagging. Certainly we’ve all used tags somewhere on the internet and i really like this kind of taxonomies. It’s way better than a fixed folder structure.

So, i can now tag all my documents without the need for an external program.

But what about sync? Those tags are stored in the extended file attributes of the Mac OS X filesystem (along with other stuff, for example if the file has been download from the web or email). git does not include those extended attributes in a repository so they will be lost.

xattr to the rescue. xattr can dump all extended attributes for all files in a directory and also can write them back.

I use the following pre-commit hook to dump all extended attributes of my archive to a file named .metadata

#!/bin/sh
 
xattr -lrx . > .metadata
git add -f .metadata

This can be a problem if only tags are modified as nothing will be committed. This can be handled by an empty commit:

git commit --allow-empty -m "New Tags

To restore them i use the following post-merge hook which is also executed after a pull (i’m pretty much doing only pulls on this repository anyway).

#!/usr/bin/env ruby
# Be careful, this can be something you don't want:
# strip all existing extended attributes
system("xattr -cr .")
 
pattern_header = /([^\0]+): (.+):/
pattern_data = /\d{8} (.+) +\|.+\|/
 
data, current_file, current_attribute = '', nil, nil
 
File.readlines('.metadata').each do |line|  
  # collect hex data
  if(m = pattern_data.match(line) and current_file)
    m = pattern_data.match line
    data += m[1].to_s.strip if m and m[1]  
  # starting hex data for a new file
  elsif(m = pattern_header.match(line))
    # we have some data for the current file
    if current_file and data != ''
      system("xattr -wx #{current_attribute} #{data.gsub(/ /, '')} \"#{current_file}\"")
    end   
    data, current_file, current_attribute = '', m[1], m[2] 
  elsif current_file   
    m = pattern_data.match line
    data += m[1].to_s.strip if m and m[1]  
  end
end

This hook is pretty simple and one can surely think of better ways for storing (and / or parsing) the data and add some error handling, but this works quite well for my purpose.

This hook also stores every extended attribute. If you’re only interested in meta tags, than only sync the “com.apple.metadata:_kMDItemUserTags” attribute.

Filed in Apple, English posts | Comments (2) »