第 10 章 扩展 Neo4j 服务器

提示

如果你想完全控制你的API，你需要多花心思，并理解这样做的风险，而Neo4j服务端也可以通过JAX-RS提供非托管的扩展。

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<dependency>

<groupId>org.neo4j</groupId>

<artifactId>server-api</artifactId>

<version>${neo4j-version}</version>

</dependency>

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@Description( "An extension to the Neo4j Server for getting all nodes or relationships")

publicclassGetAll extendsServerPlugin

{

@Name( "get_all_nodes")

@Description( "Get all nodes from the Neo4j graph database")

@PluginTarget( GraphDatabaseService.class)

publicIterable<Node> getAllNodes( @SourceGraphDatabaseService graphDb )

{

returnGlobalGraphOperations.at( graphDb ).getAllNodes();

}

@Description( "Get all relationships from the Neo4j graph database")

@PluginTarget( GraphDatabaseService.class)

publicIterable<Relationship> getAllRelationships( @SourceGraphDatabaseService graphDb )

{

returnGlobalGraphOperations.at( graphDb ).getAllRelationships();

}

}

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publicclassShortestPath extendsServerPlugin

{

@Description( "Find the shortest path between two nodes.")

@PluginTarget( Node.class)

publicIterable<Path> shortestPath(

@SourceNode source,

@Description( "The node to find the shortest path to.")

@Parameter( name = "target") Node target,

@Description( "The relationship types to follow when searching for the shortest path(s). "+

"Order is insignificant, if omitted all types are followed.")

@Parameter( name = "types", optional = true) String[] types,

@Description( "The maximum path length to search for, default value (if omitted) is 4.")

@Parameter( name = "depth", optional = true) Integer depth )

{

Expander expander;

if( types == null)

{

expander = Traversal.expanderForAllTypes();

}

else

{

expander = Traversal.emptyExpander();

for( inti = 0; i < types.length; i++ )

{

expander = expander.add( DynamicRelationshipType.withName( types[i] ) );

}

}

PathFinder<Path> shortestPath = GraphAlgoFactory.shortestPath(

expander, depth == null? 4: depth.intValue() );

returnshortestPath.findAllPaths( source, target );

}

}

提示

确保通过Maven或者 `jar -cvf myext.jar *`编译时，目录列表被保留在jar文件中，确定jar目录代替指定的单个文件。

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org.neo4j.examples.server.plugins.GetAll

org.neo4j.examples.server.plugins.DepthTwo

org.neo4j.examples.server.plugins.ShortestPath

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curl -vhttp://localhost:7474/db/data/

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{

"extensions-info": "http://localhost:7474/db/data/ext",

"node": "http://localhost:7474/db/data/node",

"node_index": "http://localhost:7474/db/data/index/node",

"relationship_index": "http://localhost:7474/db/data/index/relationship",

"reference_node": "http://localhost:7474/db/data/node/0",

"extensions_info": "http://localhost:7474/db/data/ext",

"extensions": {

"GetAll": {

"get_all_nodes": "http://localhost:7474/db/data/ext/GetAll/graphdb/get_all_nodes",

"get_all_relationships": "http://localhost:7474/db/data/ext/GetAll/graphdb/getAllRelationships"

}

}

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curl http://localhost:7474/db/data/ext/GetAll/graphdb/get_all_nodes

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{

"extends": "graphdb",

"description": "Get all nodes from the Neo4j graph database",

"name": "get_all_nodes",

"parameters": [ ]

}

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curl -X POST http://localhost:7474/db/data/ext/GetAll/node/123/shortestPath\

-H "Content-Type: application/json"\

-d '{"target":"http://localhost:7474/db/data/node/456&depth=5"}'

警告

这是一把双刃剑，它允许用户随意部署 JAX-RS类到服务端，因此你要小心使用。特别是你应该明白，他会轻易的就占用服务端的大量的堆空间，降低你可能不关心的服务端的性能。

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publicMyCoolService( @ContextGraphDatabaseService database )

{

// Have fun here, but be safe!

}

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@Path( "/helloworld")

publicclassHelloWorldResource

{

privatefinalGraphDatabaseService database;

publicHelloWorldResource( @ContextGraphDatabaseService database )

{

this.database = database;

}

@GET

@Produces( MediaType.TEXT_PLAIN )

@Path( "/{nodeId}")

publicResponse hello( @PathParam( "nodeId") longnodeId )

{

// Do stuff with the database

returnResponse.status( Status.OK ).entity(

( "Hello World, nodeId="+ nodeId ).getBytes() ).build();

}

}

提示

确保通过Maven或者 jar -cvf myext.jar *构建的jar文件包括了目录清单，确保用jar目录代替单个文件。

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#包含JAXRS资源的JAXRS包被逗号分隔开，一个包名对应一个挂载点。

org.neo4j.server.thirdparty_jaxrs_classes=org.neo4j.examples.server.unmanaged=/examples/unmanaged

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curl http://localhost:7474/examples/unmanaged/helloworld/123

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Hello World, nodeId=123