在本文中,我們將瞭解如何直接從智慧合約生成Java Wrapper類以與Java中的智慧合約進行互動。從智慧合約生成Java Wrapper類有不同的方法:1. Web3j命令列工具和solc2. Web3j命令列工具和Truffle構建生成的工件3. web3j-maven-plugin4. web3j-gradle-plugin為了演示如何使用上述方法,本教程使用以下智慧合約將文件公證到以太坊區塊鏈上的登錄檔中。DocumentRegistry.solpragma solidity ^0.5.6;/*** @dev Smart Contract responsible to notarize documents on the Ethereum Blockchain*/contract DocumentRegistry { struct Document { address signer; // Notary uint date; // Date of notarization bytes32 hash; // Document Hash } /** * @dev Storage space used to record all documents notarized with metadata */ mapping(bytes32 => Document) registry; /** * @dev Notarize a document identified by its 32 bytes hash by recording the hash, the sender and date in the registry * @dev Emit an event Notarized in case of success * @param _documentHash Document hash */ function notarizeDocument(bytes32 _documentHash) external returns (bool) { registry[_documentHash].signer = msg.sender; registry[_documentHash].date = now; registry[_documentHash].hash = _documentHash; emit Notarized(msg.sender, _documentHash); return true; } /** * @dev Verify a document identified by its hash was noterized in the registry. * @param _documentHash Document hash * @return bool if document was noterized previsouly in the registry */ function isNotarized(bytes32 _documentHash) external view returns (bool) { return registry[_documentHash].hash == _documentHash; } /** * @dev Definition of the event triggered when a document is successfully notarized in the registry */ event Notarized(address indexed _signer, bytes32 _documentHash);}web3j命令列工具和solc
第一種方法使用solc生成Smart合約ABI和bytecode,並將這兩個檔案作為輸入提供給web3j-cli以生成Wrapper。1、安裝solc並驗證版本安裝solc並執行以下命令以確保solc版本大於或等於0.5.6(智慧合約中指定的版本)。$ solc --versionsolc, the solidity compiler commandline interfaceVersion: 0.5.9+commit.c68bc34e.Linux.g++2、安裝Web3J CLI要安裝web3j cli,請從專案儲存庫的“釋出”頁面的“下載”部分下下載zipfile/tarball,或透過homebrew為MacOS使用者或透過aur為Arch Linux使用者下載zipfile/tarball。brew tap web3j/web3jbrew install web3jweb3j要透過zipfile執行,解壓縮並執行二進位制檔案,您可能還需要將二進位制檔案新增到PATH中:$ unzip web3j-4.3.0.zip creating: web3j-4.3.0/lib/ inflating: web3j-4.3.0/lib/core-1.0.2-all.jar creating: web3j-4.3.0/bin/ inflating: web3j-4.3.0/bin/web3j inflating: web3j-4.3.0/bin/web3j.bat$ ./web3j-<version>/bin/web3j _ _____ _ _ | | |____ (_) (_)__ _____| |__ / /_ _ ___\ \ /\ / / _ \ '_ \ \ \ | | | / _ \\ V V / __/ |_) |.___/ / | _ | || (_) | \_/\_/ \___|_.__/ \____/| |(_)|_| \___/ _/ | |__/Usage: web3j version|wallet|solidity ...3、使用solc編譯智慧合約給定我們的Solidity檔案DocumentRegistry.sol,solc <sol> --bin --abi --optimize -o <output>命令編譯智慧合約並在同一目錄中生成兩個新檔案:$ solc DocumentRegistry.sol --bin --abi --optimize -o ./Compiler run successful. Artifact(s) can be found in directory ./.$ ls -ltotal 12-rw-rw-r-- 1 gjeanmart gjeanmart 565 Jun 24 13:42 DocumentRegistry.abi-rw-rw-r-- 1 gjeanmart gjeanmart 676 Jun 24 13:42 DocumentRegistry.bin-rw-rw-r-- 1 gjeanmart gjeanmart 1488 Jun 24 13:40 DocumentRegistry.solDocumentRegistry.bin:二進位制檔案,智慧合約的位元組碼DocumentRegistry.abi:智慧合約的ABI(應用程式二進位制介面),它以JSON格式定義介面。4、使用web3j-cli生成包裝器使用ABI和bytecode(在步驟3中生成)和web3j-cli(在步驟2中安裝),我們現在可以使用以下命令生成我們的智慧合約的Java Wrapper:web3j solidity generate -a=<abiFile> -b=<binFile> -o=<destinationFileDir> -p=<packageName>示例:$ web3j solidity generate -a DocumentRegistry.abi -b DocumentRegistry.bin -o . -p me.gjeanmart.tutorials.javaethereum.wrapper _ _____ _ _ | | |____ (_) (_)__ _____| |__ / /_ _ ___\ \ /\ / / _ \ '_ \ \ \ | | | / _ \ \ V V / __/ |_) |.___/ / | _ | || (_) | \_/\_/ \___|_.__/ \____/| |(_)|_| \___/ _/ | |__/Generating me.gjeanmart.tutorials.javaethereum.wrapper.DocumentRegistry ... File written to .因此,您應該看到生成到資料夾/.java中的Java Wrapper檔案,您可以將其複製到專案的src / main / java /資料夾中。./me/gjeanmart/tutorials/javaethereum/wrapper/DocumentRegistry.javaWeb3j命令列工具和Truffle artefacts
Truffle是最著名的框架之一,可幫助您使用以太坊開發、測試和部署。 我們可以使用Truffle使用Web3j命令列工具生成的artefacts來建立wrapper類。1、安裝TruffleTruffle可作為npm wrapper提供。$ npm install truffle -g- Fetching solc version list from solc-bin. Attempt #1+ admin@chaindailyadded 27 packages from 439 contributors in 11.636s$ truffle versionTruffle v5.0.24 (core: 5.0.24)Solidity v0.5.0 (solc-js)Node v10.15.3Web3.js v1.0.0-beta.372、初始化新的Truffle專案要初始化Truffle專案,請在新資料夾中使用truffle init命令。該命令建立資料夾contract /,migration /和test /,以及檔案truffle-config.js。$ mkdir truffle$ cd truffle$ truffle init? Preparing to download? Downloading? Cleaning up temporary files? Setting up boxUnbox successful. Sweet!Commands: Compile: truffle compile Migrate: truffle migrate Test contracts: truffle test$ ls -ltotal 20drwxrwxr-x 2 gjeanmart gjeanmart 4096 Jun 24 14:25 contractsdrwxrwxr-x 2 gjeanmart gjeanmart 4096 Jun 24 14:25 migrationsdrwxrwxr-x 2 gjeanmart gjeanmart 4096 Jun 24 14:25 test-rw-rw-r-- 1 gjeanmart gjeanmart 4233 Jun 24 14:25 truffle-config.js3、將合同新增到資料夾合約中將智慧合約源documentregistry.sol複製到資料夾contracts中。4、編譯合約使用命令truffle compile編譯智慧合約,此命令生成一個新的資料夾build/contracts/,其中包含每個編譯的智慧合約的truffle artefact。$ truffle compileCompiling your contracts...===========================> Compiling ./contracts/DocumentRegistry.sol> Compiling ./contracts/Migrations.sol> Artifacts written to /home/gjeanmart/workspace/tutorials/java-ethereum-wrapper/truffle/build/contracts> Compiled successfully using: - solc: 0.5.8+commit.23d335f2.Emscripten.clang$ ls -l build/contracts/total 136-rw-rw-r-- 1 gjeanmart gjeanmart 79721 Jun 24 14:33 DocumentRegistry.json-rw-rw-r-- 1 gjeanmart gjeanmart 54043 Jun 24 14:33 Migrations.json5、從Truffle Artefact生成智慧合約Java Wrapper最後,web3j-cli提供了一種方法,可以使用以下命令直接從truffle編譯的Truffle artefact結果生成Wrapper:$ web3j truffle generate ./build/contracts/DocumentRegistry.json -o . -p me.gjeanmart.tutorials.javaethereum.wrapper _ _____ _ _ | | |____ (_) (_)__ _____| |__ / /_ _ ___\ \ /\ / / _ \ '_ \ \ \ | | | / _ \ \ V V / __/ |_) |.___/ / | _ | || (_) | \_/\_/ \___|_.__/ \____/| |(_)|_| \___/ _/ | |__/Generating me.gjeanmart.tutorials.javaethereum.wrapper.DocumentRegistry ... File written to .因此,您應該看到生成到<packagefolders> /。java_資料夾中的Java Wrapper檔案,您可以將其複製到專案的src / main / java /資料夾中。./me/gjeanmart/tutorials/javaethereum/wrapper/DocumentRegistry.java注意:使用Truffle,您可以做的比本文中顯示的更多,例如部署指令碼(遷移)、多網路配置、測試、除錯。web3j-maven-plugin下一個解決方案比前兩個解決方案更優雅,因為我們不必安裝webj-cli並將檔案複製到原始檔夾。我們可以使用Maven和web3j-maven-plugin直接在Java專案中使用此方法。以下步驟假定您已建立Maven專案。1、先決條件安裝solc並執行以下命令以確保solc版本大於或等於0.5.6(智慧合約中指定的版本)。$ solc --versionsolc, the solidity compiler commandline interfaceVersion: 0.5.9+commit.c68bc34e.Linux.g++2、將智慧合約複製到資料夾src / main / resources中將Smart Contract源DocumentRegistry.sol複製到Maven專案的src / main / resources資料夾中。3、配置Maven以在generate-sources階段生成Wrapper在此步驟中,我們配置兩個Maven外掛:web3j - Maven的外掛第一個外掛與前兩個方法相同,但與Maven整合。首先,我們將外掛配置為在進入專案的generate-sources階段時自動執行。其次我們配置外掛引數:· packageName:要應用於生成的Wrapper類的包名稱· sourceDestination:目標資料夾,用於移動生成的Wrapper類· soliditySourceFiles:在何處查詢Smart Contract原始檔建立輔助性Maven的外掛第二個外掛將sourceDestination資料夾新增到類路徑中,以便我們可以匯入生成的Wrapper類pom.xml<build> <plugins> <plugin> <groupId>org.web3j</groupId> <artifactId>web3j-maven-plugin</artifactId> <version>4.2.0</version> <executions> <execution> <id>generate-sources-web3j</id> <phase>generate-sources</phase> <goals> <goal>generate-sources</goal> </goals> <configuration> <packageName>me.gjeanmart.tutorials.javaethereum.contracts.generated</packageName> <sourceDestination>${basedir}/target/generated-sources/contracts</sourceDestination> <soliditySourceFiles> <directory>${basedir}/src/main/resources</directory> <includes> <include>**/*.sol</include> </includes> </soliditySourceFiles> </configuration> </execution> </executions> </plugin> <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>build-helper-maven-plugin</artifactId> <executions> <execution> <id>add-source</id> <phase>generate-sources</phase> <goals> <goal>add-source</goal> </goals> <configuration> <sources> <source>${basedir}/target/generated-sources/contracts</source> </sources> </configuration> </execution> </executions> </plugin> </plugins></build>4、執行Maven生成源最後,使用mvn clean package(包括generate-sources階段)構建Maven專案。因此,我們可以看到Java Wrapper已生成到/target/generated-sources/contracts/me/gjeanmart/tutorials/javaethereum/contracts/generated/DocumentRegistry.java並自動新增到類路徑中。
Web3J Gradle外掛
最後一個方法與之前使用Maven的方法類似,但使用的是Gradle。
1、先決條件
安裝solc並執行以下命令以確保solc版本大於或等於0.5.6(智慧合約中指定的版本)。
$ solc --version
solc, the solidity compiler commandline interface
Version: 0.5.9+commit.c68bc34e.Linux.g++
2、將智慧合約放入資料夾src / main / solidity
將Smart Contract源DocumentRegistry.sol複製到Gradle專案的src / main / solidity資料夾中。
3、配置Gradle以在構建期間生成Wrapper首先將web3j-gradle外掛匯入build.gradle檔案。
plugins {
id 'org.web3j' version '4.3.0'
}
然後我們可以配置外掛來為生成的wrapper類指定包名稱和目標資料夾:
web3j {
generatedPackageName = 'me.gjeanmart.tutorials.javaethereum.contracts.generated'
generatedFilesBaseDir = "$buildDir/contracts"
}
要使用系統安裝的solc版本而不是與外掛捆綁的版本,請將以下行新增到build.gradle:
solidity {
executable = "solc"
}
build.gradle
/*
* This file was generated by the Gradle 'init' task.
*
* This generated file contains a sample Java Library project to get you started.
* For more details take a look at the Java Libraries chapter in the Gradle
* user guide available at https://docs.gradle.org/5.0/userguide/java_library_plugin.html
*/
plugins {
// Apply the java-library plugin to add support for Java Library
id 'java-library'
id 'org.web3j' version '4.3.0'
}
repositories {
// Use jcenter for resolving your dependencies.
// You can declare any Maven/Ivy/file repository here.
jcenter()
}
dependencies {
// This dependency is exported to consumers, that is to say found on their compile classpath.
api 'org.apache.commons:commons-math3:3.6.1'
// This dependency is used internally, and not exposed to consumers on their own compile classpath.
implementation 'com.google.guava:guava:26.0-jre'
implementation 'org.web3j:core:4.3.0'
// Use JUnit test framework
testImplementation 'junit:junit:4.12'
}
web3j {
generatedPackageName = 'me.gjeanmart.tutorials.javaethereum.contracts.generated'
generatedFilesBaseDir = "$buildDir/contracts"
}
solidity {
executable = "solc"
}
4、執行gradle構建
在最後一步中,我們使用./gradlew tasks執行構建--all並驗證我們生成的wrapper類是否已生成。