Book review: Java Persistence With Hibernate (Second Edition)

A really nice book about Hibernate and its internals. It starts with the ORM concept, problems this concept tries to solve and main trade-offs. Authors introduce a simple auction application and explain how to design domain models and their relationships using Hibernate and this application all around the book. There are many approaches to solve the same problem and this book shows them and explains the pros and cons behind the solutions you can apply. A few chapters go even beyond the Hibernate itself by giving overview of the fundamental knowledge of database transactions, ACID attributes, locks, isolation levels and caching.

This is my first book in Hibernate and I had had rough knowledge before I read it. It helped me to structure my knowledge, helped me to look under the hood and see how things actually work. I finally understood those occasional exceptions we got at my previous project and parts which were designed in a wrong way. However, there is one thing I would like to see better explained - a second-level cache. It would be nice to see it earlier in the book and get more examples and details about its applications and trade-offs.

I would definitely recommend this book to all levels of engineers. It is also a good source to refresh your Hibernate knowledge or to come back later if you need some clarifications.

Time spent on the book: ~39 hours

Triangle rasterization under the hood (the old-school approach)

I didn't find a single source which would gave me a complete and clear picture of how to rasterize a triangle in a simplest way.

So, here's my attempt to put everything in order.

Consider, that we know how to draw a line and nothing more. Here's the corresponding method declaration for it:

void drawLine(int x0, int y0, int x1, int y1, Color color);

We need to implement a method which will draw a triangle and fill it with a specified color. Here's the corresponding method declaration:

void drawTriangle(Vec2 v0, Vec2 v1, Vec2 v2, Color color);

Here's the visual representation of what this method should do:

Initial vertices

Rasterized triangle

drawTriangle(v0, v1, v2, Color.BLACK)

============================>

JLV 1.4.0 released

Eclipse Marketplace: http://marketplace.eclipse.org/content/jlv

Project's page: https://github.com/rdiachenko/jlv#information

Release notes:

• made plugin work on Eclipse 4.6
• added support for logback and log4j2
• redesigned detailed log view

How to connect Sony LT25i to Android Studio under Fedora 24

0. Turn on USB debugging mode via Settings > Developer options

1. Connect smartphone to PC via USB and get vendor's id

$ lsusb
...
Bus 003 Device 013: ID 0fce:6186 Sony Ericsson Mobile Communications AB
...

Note: here vendor's id is: 0fce

2. Create udev rules file to allow Fedora to detect device

$ cat /etc/udev/rules.d/51-android.rules

SUBSYSTEM=="usb", ATTR{idVendor}=="0fce", MODE="0666", GROUP="rdiachenko"

Note: here you need to change GROUP onto your own

Minesweeper for Linux (just for fun)

Much time has been passed since I last played minesweeper on my Windows machine in the campus... A lot has been changed since that time. Now I use Linux and I'm not in the campus any more :) I just thought: why not to implement this cool game on my own...

Here's what I have now (sources and README):

In this post I would like to share with some interesting moments I faced with during implementation.

How many numbers in the given interval with a bit set

Problem: given two numbers a and b find how many numbers with a bit x set are there in the interval [a,b].

Example:

Input: 5 8 2

Output: 3

Explanation:

5 = 0101
6 = 0110
7 = 0111
8 = 1000

The second bit (starting from the least significant bit with index 0) is set only in numbers 5, 6 and 7, so there are 3 numbers in the interval [5, 8] with the second bit set.

Solution:

Remove all merged local branches in Git except master

$ git branch
  a
  b
  c
* master

Here, branch 'c' has not merged with master yet. Let's remove all merged branches:

$ git branch --merged master | grep -v master | xargs git branch -d
Deleted branch a (was ebb9040).
Deleted branch b (was ebb9040).

$ git branch
  c
* master

A fast way to find out whether two elements in matrix share the same diagonal

Let's have the following matrix:

     1 2 3 4 5
     -----------
1 | 0 0 0 0 0
2 | 0 0 1 0 0
3 | 0 0 0 0 0
4 | 1 0 0 0 0
5 | 0 0 0 0 0

with two points: (x1, y1) = (2, 3) and (x2, y2) = (4, 1).

The fastest way to find out whether these two points share the same diagonal is the result of this expression:

bool result = (x1 + y1 == x2 + y2) or (x1 - y1 == x2 - y2)

Now let's complicate the task. Given matrix n x n with m points, find the minimum number of diagonals which contain at least two points. The first line of the input contains: n m. The next m lines contain points with coordinates (xi, yi).

dmalloc: compiling and installing a dynamic (shared) library

See the previous post: dmalloc: compiling and installing a static library

"dmalloc.h:484:7: error: expected identifier or..." problem is already solved in that post.

Now let's compile and install a shared library

dmalloc-5.5.2]$ ./configure --enable-shlib

dmalloc-5.5.2]$ make shlib
...
gcc -g -O2 -DHAVE_STDARG_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_UNISTD_H=1 -DHAVE_SYS_MMAN_H=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_W32API_WINBASE_H=0 -DHAVE_W32API_WINDEF_H=0 -DHAVE_SYS_CYGWIN_H=0 -DHAVE_SIGNAL_H=1 -I. -I. -c dmalloc_argv.c -o ./dmalloc_argv.o
rm -f dmalloc
gcc -o aout dmalloc.o dmalloc_argv.o compat.o env.o \
-L.
mv aout dmalloc
rm -f libdmalloc.so libdmalloc.so.t
ld -shared --whole-archive -soname libdmalloc.so -o libdmalloc.so.t libdmalloc.a arg_check.o compat.o dmalloc_rand.o dmalloc_tab.o env.o heap.o chunk.o error.o malloc.o
ld: libdmalloc.a(arg_check.o): relocation R_X86_64_32 against `.rodata.str1.8' can not be used when making a shared object; recompile with -fPIC
libdmalloc.a(arg_check.o): error adding symbols: Bad value
Makefile:259: recipe for target 'libdmalloc.so' failed
make: *** [libdmalloc.so] Error 1

dmalloc: compiling and installing a static library

dmalloc - http://dmalloc.com/

Installation (on Fedora 21 x86_64)

$ uname -irs

Linux 3.18.3-201.fc21.x86_64 x86_64

$ tar -zxvf dmalloc-5.5.2.tgz
dmalloc-5.5.2]$ cd dmalloc-5.5.2/
dmalloc-5.5.2]$ ./configure
configure: configurations for the dmalloc library
configure: build utilities
checking for gcc... gcc
...
checking for strtok... yes
configure: creating ./config.status
config.status: creating Makefile
config.status: creating conf.h
config.status: executing dmalloc.h.2 commands
config.status: executing settings.h commands
configure: 
configure: Please check-out Makefile and conf.h to make sure that
configure: sane configuration values were a result.
configure: 
configure: You may want to change values in settings.h before
configure: running 'make'.
configure: 
configure: To run the basic library tests, you can execute:
configure:   make light
configure: or
configure:   make heavy
configure:

dmalloc-5.5.2]$ make
rm -f dmalloc.h dmalloc.h.t
cat ./dmalloc.h.1 dmalloc.h.2 ./dmalloc.h.3 > dmalloc.h.t
mv dmalloc.h.t dmalloc.h
rm -f arg_check.o
gcc -g -O2  -DHAVE_STDARG_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_UNISTD_H=1 -DHAVE_SYS_MMAN_H=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_W32API_WINBASE_H=0 -DHAVE_W32API_WINDEF_H=0 -DHAVE_SYS_CYGWIN_H=0 -DHAVE_SIGNAL_H=1  -I. -I.  -c arg_check.c -o ./arg_check.o
In file included from /usr/include/string.h:634:0,
                 from arg_check.c:33:
dmalloc.h:484:7: error: expected identifier or ‘(’ before ‘__extension__’
 char *strndup(const char *string, const DMALLOC_SIZE len);
       ^
Makefile:362: recipe for target 'arg_check.o' failed
make: *** [arg_check.o] Error 1