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Neo4j Graph Database Fundamentals · Pelajaran

Prosedur Tersimpan dan UDF

Pelajari cara menulis dan menerapkan prosedur tersimpan khusus serta fungsi yang ditentukan pengguna untuk merangkum logika kompleks dan memperluas Cypher.

Prosedur Tersimpan dan UDF adalah pelajaran Neo4j Graph Database Fundamentals gratis di CoddyKit. Ini adalah pelajaran 1 dari 4. Kamu bisa membaca pelajaran lengkapnya di bawah secara gratis — lalu praktikkan langsung di browser dengan editor kode bawaan dan tutor AI 24/7. Ini adalah bagian dari jalur belajar Neo4j Graph Database Fundamentals, dan progresmu tersinkronisasi di web dan aplikasi CoddyKit. Kursus Neo4j Graph Database Fundamentals mencakup 4 pelajaran total.

Bagian dari pelajaran ini belum diterjemahkan dan ditampilkan dalam bahasa Inggris.

Extending Neo4j's Capabilities

Welcome to extending Neo4j! Sometimes, Cypher isn't enough for complex logic or specific integrations. That's where custom code comes in.

Neo4j allows you to extend its functionality using Stored Procedures and User-Defined Functions (UDFs), typically written in Java.

  • Stored Procedures perform actions, like creating nodes or running complex algorithms.
  • User-Defined Functions (UDFs) return values, just like built-in Cypher functions.

They encapsulate complex logic, improve query readability, and boost performance for repetitive tasks.

Procedures vs. User-Defined Functions

It's crucial to understand the difference between procedures and UDFs:

  • Stored Procedures:
    - Called with CALL package.procedure()
    - Can perform side effects (create, update, delete data)
    - Return tabular results (rows and columns)
    - Can access the graph database directly
  • User-Defined Functions (UDFs):
    - Called within Cypher expressions (e.g., RETURN my.udf(n.property))
    - Must be pure functions (no side effects)
    - Return a single scalar value (e.g., string, number, boolean, list)
    - Cannot modify the graph or access it directly

Stored Procedure Anatomy (Java)

Stored procedures are Java classes compiled into a JAR file. They use specific Neo4j annotations.

Here's the basic structure for a simple procedure that doesn't take any parameters and returns a string:

package com.coddykit;

import org.neo4j.procedure.Procedure;
import org.neo4j.procedure.Name;
import org.neo4j.procedure.Description;
import org.neo4j.graphdb.Result;
import java.util.stream.Stream;

public class MyProcedures {

    // Define the output record structure
    public static class StringOutput {
        public String value;

        public StringOutput(String value) {
            this.value = value;
        }
    }

    @Procedure(value = "my.hello")
    @Description("Returns a simple greeting.")
    public Stream<StringOutput> hello() {
        return Stream.of(new StringOutput("Hello from CoddyKit!"));
    }
}

Key Elements of a Procedure

Let's break down the previous code:

  • @Procedure(value = "my.hello"): This annotation declares a method as a stored procedure and defines its full name (my.hello).
  • @Description: Provides a description visible in Neo4j Browser.
  • Output Class (StringOutput): Procedures return a Stream of custom objects. Each object represents a row in the result, and its public fields become the column names.
  • Stream<StringOutput>: The return type for procedures.

This Java code is ready to be compiled into a JAR and deployed.

Deploying Your Custom Procedure

To make your Java procedure available in Neo4j, you need to compile it and place the resulting JAR file into the database's plugins directory.

Steps:

  1. Compile your Java code into a JAR file (e.g., my-procedures.jar).
  2. Copy the JAR file into your Neo4j installation's plugins folder.
  3. Restart your Neo4j database instance.

After restarting, Neo4j will discover and register your new procedures and functions.

Calling a Stored Procedure

Once deployed, you can call your procedure using the CALL keyword in Cypher. Let's try calling our my.hello procedure:

CALL my.hello();

User-Defined Function (UDF) Anatomy

UDFs are similar to procedures but have different annotations and return types. They are designed to be used inline within Cypher expressions.

Here's the basic structure for a UDF that takes a string and returns a modified string:

package com.coddykit;

import org.neo4j.procedure.UserFunction;
import org.neo4j.procedure.Name;
import org.neo4j.procedure.Description;

public class MyFunctions {

    @UserFunction("my.capitalize")
    @Description("Capitalizes the first letter of an input string.")
    public String capitalize(@Name("input") String input) {
        if (input == null || input.isEmpty()) {
            return input;
        }
        return Character.toUpperCase(input.charAt(0)) + input.substring(1);
    }
}

Key Elements of a UDF

Let's look at the UDF's components:

  • @UserFunction("my.capitalize"): This annotation declares a method as a UDF and defines its full name (my.capitalize).
  • @Name("input"): Specifies the name for the parameter when used in Cypher.
  • Return Type: UDFs return a single scalar value (e.g., String, Long, Boolean, List<String>). They do not return a Stream or custom output objects.

Like procedures, this Java code must be compiled into a JAR and deployed to the plugins folder.

Calling a User-Defined Function

After deploying your UDF, you can use it directly within Cypher queries as part of an expression. It behaves just like built-in functions.

Let's use our my.capitalize UDF:

RETURN my.capitalize("hello world");

// Or with graph data:
MATCH (p:Person)
RETURN p.name, my.capitalize(p.name) AS CapitalizedName;

Quick Check: Procedures & UDFs

Which of the following statements is TRUE regarding Neo4j Stored Procedures and User-Defined Functions (UDFs)?

Recap & Next Steps

You've learned how to extend Neo4j with custom Java code!

  • Stored Procedures execute complex actions, return tabular results, and are called with CALL.
  • User-Defined Functions (UDFs) return single scalar values, are pure functions (no side effects), and are used inline in Cypher expressions.
  • Both require Java code, specific Neo4j annotations, compilation into a JAR, and deployment to the Neo4j plugins directory.

These powerful extensions allow you to integrate custom logic, algorithms, and external services directly into your Neo4j environment, significantly expanding its capabilities.

Pertanyaan yang Sering Diajukan

Apakah pelajaran “Prosedur Tersimpan dan UDF” gratis?

Ya — teks lengkap “Prosedur Tersimpan dan UDF” gratis dibaca di sini di web. Untuk praktiknya secara interaktif (editor kode bawaan dan tutor AI 24/7) dan buka sisa kursus Neo4j Graph Database Fundamentals, upgrade ke CoddyKit PRO. Kursus Neo4j Graph Database Fundamentals mencakup 4 pelajaran total.

Apa yang akan aku pelajari di “Prosedur Tersimpan dan UDF”?

Pelajari cara menulis dan menerapkan prosedur tersimpan khusus serta fungsi yang ditentukan pengguna untuk merangkum logika kompleks dan memperluas Cypher. Kamu berlatih Neo4j Graph Database Fundamentals dengan kode praktik yang langsung kamu jalankan di browser, dan tutor AI 24/7 menjawab pertanyaanmu saat kamu mengerjakan pelajaran ini.

Apakah aku perlu pengalaman untuk memulai Neo4j Graph Database Fundamentals?

Tidak diperlukan pengalaman sebelumnya. Neo4j Graph Database Fundamentals di CoddyKit dirancang untuk pemula hingga pelajar tingkat lanjut, jadi kamu bisa memulai di sini atau dari awal dan belajar sesuai kecepatan kamu sendiri. Ini adalah pelajaran 1 dari 4.

Berapa lama pelajaran “Prosedur Tersimpan dan UDF” memakan waktu?

Sebagian besar pelajaran CoddyKit memakan waktu sekitar 5–10 menit. Setiap pelajaran ringkas dan interaktif, jadi kamu membuat kemajuan stabil dan melanjutkan dari tempat kamu tinggalkan di web dan aplikasi.

Bisakah aku menulis dan menjalankan kode dalam pelajaran Neo4j Graph Database Fundamentals ini?

Ya. Setiap pelajaran Neo4j Graph Database Fundamentals menyertakan editor kode bawaan, jadi kamu menulis dan menjalankan kode nyata langsung di browser dan mendapatkan umpan balik AI instan — tidak diperlukan penyiapan lokal.

Semua pelajaran dalam kursus ini

  1. Prosedur Tersimpan dan UDF
  2. Integrasi dengan Alat BI dan Visualisasi
  3. Pipeline Penyerapan Data Lanjutan
  4. Pencarian Teks Lengkap dan Vektor di Neo4j
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