Fabric2.0 Java鏈碼開發實戰（Maven工程）

   本文主要介紹如何編寫Fabric 2.0的Java鏈碼，選用的是Maven工程（Gradle工程會有所不同）

基礎環境

  jdk：1.8
  maven：3.6.3
  fabric java：2.0.1

創建工程

  創建maven項目，Archetype選擇quickstart即可。

  修改pom.xml，注意配置mainClass（值爲定義的包名.類名）

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>maxisvest</groupId>
	<artifactId>fabric-java-chaincode-sample</artifactId>
	<version>1.0-SNAPSHOT</version>
    <properties>
        
        <java.version>1.8</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <fabric-chaincode-java.version>2.0.1</fabric-chaincode-java.version>
        <logback.version>1.0.13</logback.version>
        <slf4j.version>1.7.5</slf4j.version>
        <!-- Test -->
        <junit.version>4.11</junit.version>
    </properties>

    <repositories>
        <repository>
            <id>jitpack.io</id>
            <url>https://www.jitpack.io</url>
        </repository>
        <repository>
            <id>artifactory</id>
            <url>https://hyperledger.jfrog.io/hyperledger/fabric-maven</url>
        </repository>
    </repositories>

    <dependencies>

        <!-- fabric-chaincode-java -->
        <dependency>
            <groupId>org.hyperledger.fabric-chaincode-java</groupId>
            <artifactId>fabric-chaincode-shim</artifactId>
            <version>${fabric-chaincode-java.version}</version>
            <scope>compile</scope>
        </dependency>

        <dependency>
            <groupId>org.hyperledger.fabric-chaincode-java</groupId>
            <artifactId>fabric-chaincode-protos</artifactId>
            <version>${fabric-chaincode-java.version}</version>
            <scope>compile</scope>
        </dependency>


        <!-- fabric-sdk-java -->

        <!-- Logging with SLF4J & LogBack -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${slf4j.version}</version>
            <scope>compile</scope>
        </dependency>

        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>${logback.version}</version>
            <scope>runtime</scope>
        </dependency>

        <!-- Test Artifacts -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>${junit.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>20.0</version>
        </dependency>

    </dependencies>

    <build>
        <sourceDirectory>src/main/java</sourceDirectory>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.1.0</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <finalName>chaincode</finalName>
                            <transformers>
                                <transformer
                                        implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>org.example.SimpleAssetChaincode</mainClass>
                                </transformer>
                            </transformers>
                            <filters>
                                <filter>
                                    <!-- filter out signature files from signed dependencies, else repackaging fails with security ex -->
                                    <artifact>*:*</artifact>
                                    <excludes>
                                        <exclude>META-INF/*.SF</exclude>
                                        <exclude>META-INF/*.DSA</exclude>
                                        <exclude>META-INF/*.RSA</exclude>
                                    </excludes>
                                </filter>
                            </filters>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>


</project>

  編寫鏈碼SimpleAssetChaincode.java

package org.example;

import org.hyperledger.fabric.shim.ChaincodeBase;
import org.hyperledger.fabric.shim.ChaincodeStub;

import java.util.List;

public class SimpleAssetChaincode extends ChaincodeBase {

    @Override
    public Response init(ChaincodeStub stub) {
        try {
            // Get the args from the transaction proposal
            List<String> args = stub.getStringArgs();
            if (args.size() != 2) {
                newErrorResponse("Incorrect arguments. Expecting a key and a value");
            }
            // Set up any variables or assets here by calling stub.putState()
            // We store the key and the value on the ledger
            stub.putStringState(args.get(0), args.get(1));
            return newSuccessResponse();
        } catch (Throwable e) {
            return newErrorResponse("Failed to create asset");
        }
    }

    @Override
    public Response invoke(ChaincodeStub stub) {
        try {
            // Extract the function and args from the transaction proposal
            String func = stub.getFunction();
            List<String> params = stub.getParameters();
            if (func.equals("set")) {
                // Return result as success payload
                return newSuccessResponse(set(stub, params));
            } else if (func.equals("get")) {
                // Return result as success payload
                return newSuccessResponse(get(stub, params));
            }
            return newErrorResponse("Invalid invoke function name. Expecting one of: [\"set\", \"get\"");
        } catch (Throwable e) {
            return newErrorResponse(e.getMessage());
        }
    }

    private String get(ChaincodeStub stub, List<String> args) {
        if (args.size() != 1) {
            throw new RuntimeException("Incorrect arguments. Expecting a key");
        }

        String value = stub.getStringState(args.get(0));
        if (value == null || value.isEmpty()) {
            throw new RuntimeException("Asset not found: " + args.get(0));
        }
        return value;
    }

    private String set(ChaincodeStub stub, List<String> args) {
        if (args.size() != 2) {
            throw new RuntimeException("Incorrect arguments. Expecting a key and a value");
        }
        stub.putStringState(args.get(0), args.get(1));
        return args.get(1);
    }

    public static void main(String[] args) {
        new SimpleAssetChaincode().start(args);
    }

}