java - 资源规范不允许错误

Question

在 Eclipse 中运行此 Java 代码时出现以下错误。

Exception in thread "main" java.lang.Error: Unresolved compilation problems:    Resource specification not allowed here for source level below 1.7  The type Transaction is not visible     tx cannot be resolved

    at neo4jTesting.EmbeddedNeo4j.createDb(EmbeddedNeo4j.java:52)   at neo4jTesting.EmbeddedNeo4j.main(EmbeddedNeo4j.java:38)

这是代码

import java.io.File; import java.io.IOException; import org.neo4j.graphdb.Direction; import org.neo4j.graphdb.GraphDatabaseService; import org.neo4j.graphdb.Node; import org.neo4j.graphdb.Relationship; import org.neo4j.graphdb.RelationshipType; import org.neo4j.graphdb.Transaction; import org.neo4j.graphdb.factory.GraphDatabaseFactory; import org.neo4j.kernel.impl.util.FileUtils;

public class EmbeddedNeo4j {
    private static final String DB_PATH = "target/neo4j-hello-db";

    public String greeting;

    // START SNIPPET: vars
    GraphDatabaseService graphDb;
    Node firstNode;
    Node secondNode;
    Relationship relationship;
    // END SNIPPET: vars

    // START SNIPPET: createReltype
    private static enum RelTypes implements RelationshipType
    {
        KNOWS
    }
    // END SNIPPET: createReltype

    public static void main( final String[] args )
    {
        EmbeddedNeo4j hello = new EmbeddedNeo4j();
        hello.createDb();
        hello.removeData();
        hello.shutDown();
    }

    void createDb()
    {
        clearDb();
        // START SNIPPET: startDb
        graphDb = new GraphDatabaseFactory().newEmbeddedDatabase( DB_PATH );
        registerShutdownHook( graphDb );
        // END SNIPPET: startDb

        // START SNIPPET: transaction
        try ( Transaction tx = graphDb.beginTx() )
        {
            // Database operations go here
            // END SNIPPET: transaction
            // START SNIPPET: addData
            firstNode = graphDb.createNode();
            firstNode.setProperty( "message", "Hello, " );
            secondNode = graphDb.createNode();
            secondNode.setProperty( "message", "World!" );

            relationship = firstNode.createRelationshipTo( secondNode, RelTypes.KNOWS );
            relationship.setProperty( "message", "brave Neo4j " );
            // END SNIPPET: addData

            // START SNIPPET: readData
            System.out.print( firstNode.getProperty( "message" ) );
            System.out.print( relationship.getProperty( "message" ) );
            System.out.print( secondNode.getProperty( "message" ) );
            // END SNIPPET: readData

            greeting = ( (String) firstNode.getProperty( "message" ) )
                       + ( (String) relationship.getProperty( "message" ) )
                       + ( (String) secondNode.getProperty( "message" ) );

            // START SNIPPET: transaction
            tx.success();
        } finally {
            tx.finish();
        }
        // END SNIPPET: transaction
    }

    private void clearDb()
    {
        try
        {
            FileUtils.deleteRecursively( new File( DB_PATH ) );
        }
        catch ( IOException e )
        {
            throw new RuntimeException( e );
        }
    }

    void removeData()
    {
        try ( Transaction tx = graphDb.beginTx() )
        {
            // START SNIPPET: removingData
            // let's remove the data
            firstNode.getSingleRelationship( RelTypes.KNOWS, Direction.OUTGOING ).delete();
            firstNode.delete();
            secondNode.delete();
            // END SNIPPET: removingData

            tx.success();
        } finally {
            tx.finish();
        }
    }

    void shutDown()
    {
        System.out.println();
        System.out.println( "Shutting down database ..." );
        // START SNIPPET: shutdownServer
        graphDb.shutdown();
        // END SNIPPET: shutdownServer
    }

    // START SNIPPET: shutdownHook
    private static void registerShutdownHook( final GraphDatabaseService graphDb )
    {
        // Registers a shutdown hook for the Neo4j instance so that it
        // shuts down nicely when the VM exits (even if you "Ctrl-C" the
        // running application).
        Runtime.getRuntime().addShutdownHook( new Thread()
        {
            @Override
            public void run()
            {
                graphDb.shutdown();
            }
        } );
    }
    // END SNIPPET: shutdownHook }

代码来源来自 https://github.com/neo4j/neo4j/blob/master/community/embedded-examples/src/main/java/org/neo4j/examples/EmbeddedNeo4j.java

我对代码墙表示歉意，但我不知道如何用更简单的解决方案来演示该问题。

如有任何建议，我们将不胜感激。

<小时/>

编辑 1

谢谢，我已将 Java 更新到 1.7，但遇到了新错误。这是来自 Eclipse，而不是编译器。

The resource type Transaction does not implement java.lang.AutoCloseable

再次感谢您的帮助。

Answer 1

您正在使用 try-with-resources 语法 (try ( Transaction tx = graphDb.beginTx() ))，但您正在使用源进行编译等级1.6。如果可能的话，将源代码合规性更新到 1.7(Java 6 现已 EOL，Java 8 已推出公开测试版)，或使用旧式 try-catch-finally block 。