1. Environment setup

1.1. Host setup

Install VirtualBox.

Install Vagrant.


$ vagrant up
$ vagrant ssh

1.2. Box setup (Ubuntu 16.04)

Configure a dir for your produced sources and put it on your ~/.bashrc file:

$ readonly mysrc=~/src/produced; export mysrc
$ echo "!!" >> ~/.bashrc

Dotfiles configuration:

$ cd $mysrc && cat <<'EOF'|bash -e
mkdir -p $mysrc && cd $_
rm -rf dotfiles
git clone https://github.com/paulojeronimo/dotfiles
$ [ $? = 0 ] && source ~/.ambiente

Configure your name and email in ~/.gitconfig:

$ vim ~/.gitconfig

2. Basic concepts

2.1. Blockchain demo

Install node:

$ ~/src/scripts/node-setup

Download and run blockchain-demo:

$ cat <<'EOF'|bash -e
cd $mysrc
rm -rf blockchain-demo
git clone https://github.com/blockchain4devs/blockchain-demo
cd blockchain-demo
npm install
PORT=8000 ./bin/www

Open http://localhost:8000 and test. After finish your tests, press Ctrl+C at the shell running blockchain-demo.

3. Ethereum with Java

3.1. Installing Java, Maven, Gradle, and web3j

$ ~/src/scripts/java-and-tools-setup
$ vim !!
$ source ~/.sdkman/bin/sdkman-init.sh
$ cat <<'EOF'|bash
java -version
mvn -v
gradle -v

web3j setup:

$ ~/src/scripts/web3j-setup
$ vim !!
$ web3j version

3.2. web3j-demo: VersionInfo

Creating and compiling:

$ cd $mysrc
$ cp -r ../initial/web3j-demo . && cd web3j-demo
$ tree
$ vim -p pom.xml $(find . -name '*.java')
$ mvn clean package
$ git init
$ git add -A
$ git commit -m 'Initial commit'

Installing geth:

$ ~/src/scripts/ethereum-setup
$ vim !!

Running geth:

From this point it is best that you are using tmux.

$ geth --rpcapi personal,db,eth,net,web3 --rpc --rinkeby

Open another terminal and type the following command to see the size of the Rinkeby Blockchain growing on your disk (press Ctrl+C to stop):

$ watch du -hs ~/.ethereum/
Pause for a little theory …​

Attaching to a existing node:

$ geth attach ~/.ethereum/rinkeby/geth.ipc
> eth.syncing
> eth.blockNumber
> exit

Exploring the rinkeby (testnet) blockchain: open https://www.rinkeby.io/#explorer.

Installing your own blockchain explorer:

$ cd $mysrc && cat <<'EOF' | bash
rm -rf explorer
git clone https://github.com/etherparty/explorer
cd explorer
git apply ../../patches/explorer/1.patch
npm start

Seeing the patch (for curious):

$ vim ~/src/patches/explorer/1.patch

Open another terminal. Stop geth and start it again with the following parameters:

$ geth --rpcapi personal,db,eth,net,web3 --rpc --rinkeby --rpcaddr='' --rpccorsdomain "http://localhost:8000"

Open http://localhost:8000 on your host machine.

Patching web3j-demo (doing some additions):

$ cd $mysrc/web3j-demo && git apply ../../patches/web3j-demo/1.patch

Seeing the patch:

$ vim $_

Running the app (VersionInfo.java):

$ ./VersionInfo

The output produced will be something similar to:

Client version: Geth/v1.7.3-stable-4bb3c89d/linux-amd64/go1.9
Network version: 4

Commiting the changes:

$ git add -A
$ git commit -m 'Modifying pom.xml to execute VersionInfo'

3.3. Creating a wallet

$ web3j wallet create
Please enter a wallet file password: (1)
Please re-enter the password:
Please enter a destination directory location [/home/ubuntu/.ethereum/testnet/keystore]:
Creating directory: /home/ubuntu/.ethereum/testnet/keystore ...complete
Wallet file UTC--2017-11-11T03-10-00.267000000Z--6284623006d42a13050a90e343352f7e8b39ecb5.json successfully created in: /home/ubuntu/.ethereum/testnet/keystore
1 web3jtest

3.4. Viewing the wallet file

$ export wallet=`find ~/.ethereum/testnet/keystore -type f| head -n 1`
$ python -m json.tool $wallet

3.5. Requesting ETH

Copy your address (from $wallet).

Create a tweet with your address (0x + value) (Sample).

Open https://faucet.rinkeby.io/. Insert the URL of yor tweet.

requesting eth
Figure 1. Requesting ETH
eth received
Figure 2. ETH received

3.6. web3j-demo: Transfering

$ git apply ../../patches/web3j-demo/2.patch
$ git status
$ tree
$ git difftool pom.xml
$ vim src/main/java/com/paulojeronimo/web3j/Transfering.java
$ ./Transfering
Funds transfer completed...
Hash: 0x4a3c47672ebbce336861da39077c3eec1bf04db9860e51ab73adcae5ade6ae08
Block number: 1221537
eth transfered
Figure 3. ETH Transfered
$ git add -A
$ git commit -m 'Added transfering feature'

3.7. web3j-demo: Greeting

Creating the smart contract:

$ patch=../../patches/web3j-demo/3.patch
$ cat $patch
$ git apply $patch

Compiling the smart contract:

$ d=target/solidity; rm -rf $d && mkdir -p $d && solc src/main/resources/Greeter.sol --bin --abi -o $d
$ ls -l $d

Generating the Java code:

$ web3j solidity generate $d/greeter.bin $d/greeter.abi -p com.paulojeronimo.web3j.generated -o src/main/java

Compiling the Java code:

$ mvn clean package


$ ./Greeting
Greetings to the blockchain world from Paulo Jeronimo!
new Greeting from Paulo Jeronimo!


$ git add -A
$ git commit -m 'Added greeting feature'

3.9. Skills to be a better Ethereum Java Programmer

Java 8 features: Functional Programming, CompletableFuture.

Reactive Programming with RxJava.

4. Ethereum with JavaScript

First, stop the running geth. This is because we will run testrpc that listens on the same port (8545)!

Download and install the application:

$ cd $mysrc && cat <<'EOF'|bash
mkdir -p javascript-demos && cd $_
rm -rf hello_world_dapp
git clone https://github.com/mjhm/hello_world_dapp
cd hello_world_dapp
npm install

Run testrpc:

npm run testrpc

Open another shell and run:

npm run http_server

Open http://localhost:8000 on your browser and test the app.

Step by step tutorial:

GitHub code:

5. Extra references