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17_2_Accessing_Bitcoind_with_Java.md
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> **NOTE:** This is a draft in progress, so that I can get some feedback from early reviewers. It is not yet ready for learning. > **NOTE:** This is a draft in progress, so that I can get some feedback from early reviewers. It is not yet ready for learning.
This section explains how to interact with `bitcoind` using the Java programming language and the [JavaBitcoindRpcClient](https://github.com/Polve/JavaBitcoindRpcClient). This section explains how to interact with `bitcoind` using the Java programming language and the [JavaBitcoindRpcClient](https://github.com/Polve/JavaBitcoindRpcClient).
## Setting Up Java ## Setting Up Java
@ -21,7 +21,7 @@ OpenJDK 64-Bit Server VM (build 11.0.8+10-post-Debian-1deb10u1, mixed mode, shar
### Creating a Maven Project ### Creating a Maven Project
In order to prepare for Bitcoin on java, you will create a Maven project: In order to program with Bitcoin using java, you will create a Maven project:
``` ```
$ mvn archetype:generate -DgroupId=com.blockchaincommons.lbtc -DartifactId=java-project -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false $ mvn archetype:generate -DgroupId=com.blockchaincommons.lbtc -DartifactId=java-project -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false
``` ```
@ -48,7 +48,7 @@ drwxr-xr-x 15 sudo 4.0K Sep 1 13:58 ..
drwxr-xr-x 4 sudo 4.0K Sep 1 13:58 src drwxr-xr-x 4 sudo 4.0K Sep 1 13:58 src
``` ```
In order to include `JavaBitcoindRpcClient`, you must add that dependency to `<dependendencies>` in the `pom.xml` file In order to include `JavaBitcoindRpcClient`, you must add its dependency to `<dependendencies>` in the `pom.xml` file
```xml ```xml
<dependency> <dependency>
@ -57,7 +57,7 @@ In order to include `JavaBitcoindRpcClient`, you must add that dependency to `<d
<version>1.2.1</version> <version>1.2.1</version>
</dependency> </dependency>
``` ```
You need to add compiler properties to indicate what JDK version will compile the source code. You also need to add compiler properties to indicate what JDK version will compile the source code.
``` ```
<properties> <properties>
@ -88,12 +88,12 @@ If you want a sample project and some instructions on how to run it on the serve
## Building Your Connection ## Building Your Connection
To use `JavaBitcoindRpcClient`, you need to create a `BitcoindRpcClient` instance. You do this by creating a URL with arguments of username, password, IP address and port. As you'll recall, the IP address `127.0.0.1` and port `18332` should be correct for the standard testnet setup described in this documents, while you can extract the user and password from `~/.bitcoin/bitcoin.conf`. To use `JavaBitcoindRpcClient`, you need to create a `BitcoindRpcClient` instance. You do this by creating a URL with arguments of username, password, IP address and port. As you'll recall, the IP address `127.0.0.1` and port `18332` should be correct for the standard testnet setup described in this course, while you can extract the user and password from `~/.bitcoin/bitcoin.conf`.
```java ```java
BitcoindRpcClient rpcClient = new BitcoinJSONRPCClient("http://StandUp:6305f1b2dbb3bc5a16cd0f4aac7e1eba@localhost:18332"); BitcoindRpcClient rpcClient = new BitcoinJSONRPCClient("http://StandUp:6305f1b2dbb3bc5a16cd0f4aac7e1eba@localhost:18332");
``` ```
Note that you'll rneed to import the appropriate information: Note that you'll also need to import the appropriate information:
``` ```
import wf.bitcoin.javabitcoindrpcclient.BitcoinJSONRPCClient; import wf.bitcoin.javabitcoindrpcclient.BitcoinJSONRPCClient;
import wf.bitcoin.javabitcoindrpcclient.BitcoindRpcClient; import wf.bitcoin.javabitcoindrpcclient.BitcoindRpcClient;
@ -101,7 +101,7 @@ import wf.bitcoin.javabitcoindrpcclient.BitcoindRpcClient;
> **MAINNET VS TESTNET:** The port would be 8332 for a mainnet setup. > **MAINNET VS TESTNET:** The port would be 8332 for a mainnet setup.
If `rpcClient` is successfully initialized, you'll be able to send off RPC commands. If `rpcClient` is successfully initialized, you'll be able to send RPC commands.
Later, when you're all done with your `bitcoind` connection, you should close it: Later, when you're all done with your `bitcoind` connection, you should close it:
``` ```
@ -110,7 +110,7 @@ rpcClient.stop();
### Making an RPC Call ### Making an RPC Call
You'll find that the `BitcoindRpcClient` provides most of the functionality that can be accessed through `bitcoin-cli` or other RPC methods, using the same method names. You'll find that the `BitcoindRpcClient` provides most of the functionality that can be accessed through `bitcoin-cli` or other RPC methods, using the same method names, but in camelCase.
For example, to execute the `getmininginfo` command to get the block information and the difficulty on the network, you should use the `getMiningInfo()` method: For example, to execute the `getmininginfo` command to get the block information and the difficulty on the network, you should use the `getMiningInfo()` method:
```java ```java
@ -140,8 +140,7 @@ You can look up addresses on your wallet by passing the address as an argument t
AddressInfo addr1Info = rpcClient.getAddressInfo(addr1); AddressInfo addr1Info = rpcClient.getAddressInfo(addr1);
System.out.println("Address: " + addr1Info.address()); System.out.println("Address: " + addr1Info.address());
System.out.println("MasterFingerPrint: " + addr1Info.hdMasterFingerprint System.out.println("MasterFingerPrint: " + addr1Info.hdMasterFingerprint());
());
System.out.println("HdKeyPath: " + addr1Info.hdKeyPath()); System.out.println("HdKeyPath: " + addr1Info.hdKeyPath());
System.out.println("PubKey: " + addr1Info.pubKey()); System.out.println("PubKey: " + addr1Info.pubKey());
``` ```
@ -203,19 +202,20 @@ The JavaBitcoindRpcClient library has some good tools that make it easy to creat
You can create a raw transaction using the `createRawTransaction` method, passing as arguments two ArrayList objects containing inputs and outputs to be used. You can create a raw transaction using the `createRawTransaction` method, passing as arguments two ArrayList objects containing inputs and outputs to be used.
First you set up your new addresses, here an existing address on our system and a new address on our system. First you set up your new addresses, here an existing address on your system and a new address on your system.
``` ```
String addr1 = "tb1qdqkc3430rexxlgnma6p7clly33s6jjgay5q8np"; String addr1 = "tb1qdqkc3430rexxlgnma6p7clly33s6jjgay5q8np";
System.out.println("Used address addr1: " + addr1); System.out.println("Used address addr1: " + addr1);
String addr2 = rpcClient.getNewAddress(); String addr2 = rpcClient.getNewAddress();
System.out.println("Created address addr2: " + addr2); System.out.println("Created address addr2: " + addr2);
```
Then, you can use the `listUnspent` RPC to find UTXOs for the existing address.
```
List<Unspent> utxos = rpcClient.listUnspent(0, Integer.MAX_VALUE, addr1); List<Unspent> utxos = rpcClient.listUnspent(0, Integer.MAX_VALUE, addr1);
System.out.println("Found " + utxos.size() + " UTXOs (unspent transaction outputs) belonging to addr1"); System.out.println("Found " + utxos.size() + " UTXOs (unspent transaction outputs) belonging to addr1");
``` ```
Then, you can use the `listUnspent` RPC to find UTXOs for the existing address. Here's an output of all the information:
```java ```java
System.out.println("Created address addr1: " + addr1); System.out.println("Created address addr1: " + addr1);
String addr2 = rpcClient.getNewAddress(); String addr2 = rpcClient.getNewAddress();
@ -236,7 +236,7 @@ First you fill the inputs with the UTXOs you're spending:
txb.in(in); txb.in(in);
``` ```
> :warning: **WARNING:** Obviously in a real program you'd intelligently select a UTXO; here, we just grab the 0th one. > :warning: **WARNING:** Obviously in a real program you'd intelligently select a UTXO; here, we just grab the 0th one, a tactic that we'll use throughout this chapter.
Second, you fill the ouputs each with an amount and an address: Second, you fill the ouputs each with an amount and an address:
``` ```
@ -256,7 +256,7 @@ You're now ready to actually create the transaction:
### Signing a Transactions ### Signing a Transactions
You're now ready to sign transaction with the method `signRawTransactionWithKey`. This method receives as parameters an unsigned raw string transaction, the private key of the sending address, and the TxInput object. You now can sign transaction with the method `signRawTransactionWithKey`. This method receives as parameters an unsigned raw string transaction, the private key of the sending address, and the TxInput object.
```java ```java
SignedRawTransaction srTx = rpcClient.signRawTransactionWithKey( SignedRawTransaction srTx = rpcClient.signRawTransactionWithKey(
@ -270,7 +270,7 @@ You're now ready to sign transaction with the method `signRawTransactionWithKey`
### Sending a Transactiong ### Sending a Transactiong
Sending then requires the `sendRawTransaction` command: Finally, sending requires the `sendRawTransaction` command:
```java ```java
String sentRawTransactionID = rpcClient.sendRawTransaction(srTx.hex()); String sentRawTransactionID = rpcClient.sendRawTransaction(srTx.hex());
System.out.println("Sent signedRawTx (txID): " + sentRawTransactionID);``` System.out.println("Sent signedRawTx (txID): " + sentRawTransactionID);```