Question

我下载并安装了GraphDB发行版＆＃34; graphdb-free-8.5.0＆＃34; （将GraphDB作为桌面安装运行）。在GraphDB文档中，在 Section 6.5 Programming with GraphDB 中讨论了两个例子，HelloWorld.java和FamilyRelationsApp.java。

在路径mvn install中执行examples/maven-installer后，如第6.5节所述，然后我尝试编译HelloWorld.java，我收到以下错误：

HelloWorld.java:3: error: package com.ontotext.graphdb.example.util does not exist
import com.ontotext.graphdb.example.util.EmbeddedGraphDB;
                                        ^
HelloWorld.java:4: error: package org.eclipse.rdf4j.model does not exist
import org.eclipse.rdf4j.model.Value;
                              ^
HelloWorld.java:5: error: package org.eclipse.rdf4j.query does not exist
import org.eclipse.rdf4j.query.*;
^
HelloWorld.java:6: error: package org.eclipse.rdf4j.repository does not exist
import org.eclipse.rdf4j.repository.RepositoryConnection;
                                   ^
HelloWorld.java:15: error: cannot find symbol
        RepositoryConnection connection = EmbeddedGraphDB.openConnectionToTemporaryRepository("rdfs");
        ^
  symbol:   class RepositoryConnection
  location: class HelloWorld
HelloWorld.java:15: error: cannot find symbol
        RepositoryConnection connection = EmbeddedGraphDB.openConnectionToTemporaryRepository("rdfs");
                                          ^
  symbol:   variable EmbeddedGraphDB
  location: class HelloWorld
HelloWorld.java:29: error: cannot find symbol
            TupleQuery tupleQuery = connection.prepareTupleQuery(QueryLanguage.SPARQL,
            ^
  symbol:   class TupleQuery
  location: class HelloWorld
HelloWorld.java:29: error: cannot find symbol
            TupleQuery tupleQuery = connection.prepareTupleQuery(QueryLanguage.SPARQL,
                                                                 ^
  symbol:   variable QueryLanguage
  location: class HelloWorld
HelloWorld.java:36: error: cannot find symbol
            TupleQueryResult tupleQueryResult = tupleQuery.evaluate();
            ^
  symbol:   class TupleQueryResult
  location: class HelloWorld
HelloWorld.java:39: error: cannot find symbol
                BindingSet bindingSet = tupleQueryResult.next();
                ^
  symbol:   class BindingSet
  location: class HelloWorld
HelloWorld.java:42: error: cannot find symbol
                for (Binding binding : bindingSet) {
                     ^
  symbol:   class Binding
  location: class HelloWorld
HelloWorld.java:45: error: cannot find symbol
                    Value value = binding.getValue();
                    ^
  symbol:   class Value
  location: class HelloWorld
12 errors

pom.xml文件如下：

<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.ontotext.graphdb.examples</groupId>
    <artifactId>maven-installer</artifactId>
    <version>1.0.0</version>
    <packaging>pom</packaging>
    <name>Maven installer for GraphDB</name>

    <description>
        This simple pom file can be used to install the GraphDB runtime
        dependency (of the form graphdb-[edition]-runtime-x.y.z.jar) into
        the local Maven repository. Just run "mvn install".
    </description>

    <build>
        <plugins>
            <!-- Install the jar file from the lib directory -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-install-plugin</artifactId>
                <version>2.5.2</version>
                <executions>
                    <execution>
                        <id>default-install</id>
                        <phase>none</phase>
                    </execution>
                    <execution>
                        <id>install-graphdb</id>
                        <phase>install</phase>
                        <goals>
                            <goal>install-file</goal>
                        </goals>
                        <configuration>
                            <file>${project.basedir}/../../lib/graphdb-free-runtime-8.5.0.jar</file>
                            <pomFile>${project.basedir}/graphdb-free-runtime.pom</pomFile>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

正如我所说，我做了mvn install并且我成功了。但是，我不知道如何执行HelloWorld.java。我必须遵循的流程是什么才能执行GraphDB发行版中包含的java文件＆＃34; graphdb-free-8.5.0＆＃34;？

Answer 1

由于无法从Maven Central（公共Maven存储库）获得GraphDB，因此必须将GraphDB运行时jar安装到本地Maven存储库中。

为此，请转到发行版的examples / maven-installer子目录并运行：
   mvn install

好的，所以您做到了……而且它一定有效。

（旁注：that documentation seems wrong. The runtime is in Maven Central）

现在，我建议您从喜爱的IDE（Eclipse，Intellij，Netbeans等）中打开示例，作为Maven项目，并尝试从那里运行HelloWorld。

您不一定需要了解Maven的工作原理，但这会有所帮助。首先，它有助于管理外部库并为您编译项目。基本上，javac HelloWorld.java绝对不够。至少，您需要建立类路径（使用Maven安装的GraphDB JAR文件）和项目类的正确包名称。

Answer 2

在<build>内的pom.xml标记之后添加这些行：

<dependencies>
    <dependency>
        <groupId>com.ontotext.graphdb</groupId>
        <artifactId>graphdb-free-runtime</artifactId>
        <version>8.5.0</version>
    </dependency>
</dependencies>

Answer 3

不知何故，你错过了依赖关系。您确定在graphdb-free-8.5.0内声明了依赖项pom.xml吗？

developer-getting-started / HelloWorld.java无法编译

3 个答案: