Tutorial by Examples

Complete the Installation and setup to connect your app to Firebase. This will create the project in Firebase. Add the dependency for Firebase Realtime Database to your module-level build.gradle file: compile 'com.google.firebase:firebase-database:9.2.1' Configure Firebase Databa...

ThesetValue() method overwrites data at the specified location, including any child nodes. You can use this method to: Pass types that correspond to the available JSON types as follows: String Long Double Boolean Map<String, Object> List Pass a custom Java object, if the cla...

@Configuration // @Lazy - For all Beans to load lazily public class AppConf { @Bean @Lazy public Demo demo() { return new Demo(); } }

@Component @Lazy public class Demo { .... .... } @Component public class B { @Autowired @Lazy // If this is not here, Demo will still get eagerly instantiated to satisfy this request. private Demo demo; ....... }

Mongoose contains some built in functions that build on the standard find(). doc.find({'some.value':5},function(err,docs){ //returns array docs }); doc.findOne({'some.value':5},function(err,doc){ //returns document doc }); doc.findById(obj._id,function(err,doc){ //returns doc...

//'client.jade' //a button is placed down; similar in HTML button(type='button', id='send_by_button') Modify data #modify Lorem ipsum Sender //loading jQuery; it can be done from an online source as well script(src='./js/jquery-2.2.0.min.js') //AJAX request ...

i=0 while read -r line; do i=$((i+1)) done < file echo $i With a file containing: Alpha Beta Gamma Delta Epsilon The above script prints: 5

Loop n times: while [ $((i=${i:=0}+1)) -le "$n" ]; do echo line $i done Output for n=5: line 1 line 2 line 3 line 4 line 5 Manipulating decimals: $ i=3.14159; echo $((${i%.*}*2)) 6 $ i=3.14159; echo $((${i#*.}*2)) 28318

Absolute value: $ for n in -8 -2 0 3 4; do > echo $((n<0?-n:n)) > done 8 2 0 3 4 Fix variable range: $ min=2 $ max=4 $ for n in 1 2 3 4 5; do > echo $((n<min?min:n>max?max:n)) > done 2 2 3 4 4

$ ispow2() { return $((!($1!=0&&($1&$1-1)==0))); } $ i=0 $ while [ $i -lt 100 ]; do > if ispow2 $((i=i+1)); then > echo $i > fi > done 1 2 4 8 16 32 64 $1!=0 0 is not a power of 2. ($1&$1-1)==0 Unset the lowest bit. If it was the only bit...

Open routes file. Paste the following code in: Route::get('helloworld', function () { return '<h1>Hello World</h1>'; }); after going to route localhost/helloworld it displays Hello World. The routes file is located: 5.3 For Web routes/web.php For APIs routes/api.php ...

Remove the token from the client storage to avoid usage Tokens are issued by the server and you can not force browsers to delete a cookie/localStorage or control how external clients are managing your tokens. Obviously if attackers have stolen the token before logout they still could use the token,...

Mark invalid tokens, store until their expiration time and check it in every request. Blacklist breaks JWT statelessness because it requires maintaining the state. One of the benefits of JWT is no need server storage, so if you need to revoke tokens without waiting for the expiration, think also ab...

Set expiration time short and rotate tokens. Issue a new access token every few request. Use refresh tokens to allow your application to obtain new access tokens without needing to re-authenticate Refresh and access tokens access token: Authorize access to a protected resource. Limited lifetim...

Allow change user unique ID if account is compromised with a new user&password login To invalidate tokens when user changes their password or permissions, sign the token with a hash of those fields. If any of these field change, any previous tokens automatically fail to verify. The down...

This is a simple example to search in Google. It containt two parts, Feature File Step Definition File Am not going into much details here as the code itself is self explanatory. Feature File Feature:Google Key word search @mytag Scenario: search Spec Flow in Google search bar Given...

If you want to use "cmake" (see www.cmake.org), type cd [your libpng source directory] cmake . -DCMAKE_INSTALL_PREFIX=/path make make install where "/path" points to the installation directory where you want to put the libpng "lib", "include", and &quot...

This will download libpng from the official "git" repository and build it in your "libpng" directory. git clone https://github.com/glennrp/libpng.git libpng cd libpng ./autogen.sh ./configure [--prefix=/path] make install where "/path" points to the installation...

Basic architecture examples on how development for embedded systems works (i.e. IDEs, cross-compiling, downloading, in-line debugging, JTAG,...) and what would be the minimum requirements for starting. It would be worth mentioning different approaches and platforms from begginers-higher level to ad...

import { expect } from 'chai'; import { createStore } from 'redux'; describe('redux store test demonstration', () => { describe('testReducer', () => { it('should increment value on TEST_ACTION', () => { // define a test reducer with initial state: test: 0 const te...