Neo4j Java驱动手册 v4.2：连接与Cypher工作流

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"neo4j-driver-manual-4.2-java.pdf" 《Neo4j Java Driver Manual v4.2》是官方发布的针对Java开发者使用Neo4j数据库的驱动指南。这份手册详细介绍了如何与Neo4j数据库进行交互，包括驱动的安装、基本用法以及高级特性。 1. **入门 (Get started)** - **官方Java驱动介绍**：这部分简述了Neo4j官方Java驱动的作用，它是连接和操作Neo4j数据库的关键组件。 - **驱动版本与安装**：提供了不同版本的驱动信息，以及如何在项目中集成和安装 Neo4j Java 驱动。 - **“Hello, World”示例**：通过一个简单的代码示例，展示如何建立连接并执行基础查询，帮助开发者快速上手。 2. **驱动API文档 (Driver API Docs)** - 提供了详细的API参考，帮助开发者了解如何使用驱动的各种方法和类来执行操作。 3. **客户端应用 (Client applications)** - **驱动对象**：讲解了如何创建和管理Driver对象，这是与Neo4j服务器进行通信的基础。 - **连接URI**：解释了如何构造连接数据库的URI，包括主机名、端口和认证信息。 4. **认证 (Authentication)**：描述了如何设置和处理连接到数据库时的认证过程，包括用户名、密码和可能的安全策略。 5. **配置 (Configuration)**：涵盖了驱动的配置选项，如超时设置、连接池大小等，以优化性能和可靠性。 6. **日志 (Logging)**：讨论了如何配置日志系统，以便于调试和监控驱动的行为。 7. **Cypher工作流 (Cypher workflow)** - **概述**：对Cypher查询的执行流程进行了整体介绍。 - **会话 (Sessions)**：会话是执行Cypher语句的基本单元，用于管理事务和保持状态。 - **事务 (Transactions)**：介绍了显式和隐式事务，以及如何在会话中处理事务。 - **查询与结果**：讲解如何执行Cypher查询，并获取和处理返回的结果。 - **因果链和书签 (Causal chaining and bookmarks)**：用于支持因果一致性读取和跨事务跟踪。 - **路由事务与访问模式 (Routing transactions using access modes)**：说明如何根据不同的访问模式（读写）选择合适的路由策略。 - **数据库与执行上下文 (Databases and execution context)**：介绍了如何选择和切换数据库，以及设置执行上下文。 8. **类型映射 (Type mapping)**：阐述了Java对象与Cypher数据类型之间的转换规则。 9. **异常与错误处理 (Exceptions and error handling)**：讲解了如何捕获和处理驱动在运行过程中可能出现的异常。 10. **会话API (The session API)** - **简单会话 (Simple sessions)**：描述了基本的同步会话操作。 - **异步会话 (Asynchronous sessions)**：对于非阻塞的异步编程模型，提供了详细的使用指南。 - **反应式会话 (Reactive Sessions)**：针对反应式编程的会话API，强调数据流和事件驱动。 - **会话配置 (Session configuration)**：详细列出了可配置的会话参数，以满足不同需求。 11. **附录A：驱动术语 (Appendix A: Driver terminology)** - 对驱动中出现的专业术语进行了清晰的定义和解释。这份手册是开发Java应用程序与Neo4j数据库交互的重要参考，涵盖了从基础到高级的各个方面，旨在帮助开发者高效、安全地使用Neo4j。

Client applications

This section describes how to manage database connections within an application.

The Driver Object

Neo4j client applications require a Driver Object which, from a data access perspective, forms the

backbone of the application. It is through this object that all Neo4j interaction is carried out, and it

should therefore be made available to all parts of the application that require data access.

In languages where thread safety is an issue, the Driver Object can be considered thread-safe.



A note on lifecycle

Applications will typically construct a Driver Object on startup and destroy it on exit.

Destroying a Driver Object will immediately shut down any connections previously

opened via that Driver Object, by closing the associated connection pool.

This will have the consequence of rolling back any open transactions, and closing any

unconsumed results.

To construct a driver instance, a connection URI and authentication information must be supplied.

Additional configuration details can be supplied if required. The configuration details are immutable

for the lifetime of the Driver Object. Therefore, if multiple configurations are required (such as when

working with multiple database users) then multiple Driver Objects must be used.

Example 5. The driver lifecycle

import org.neo4j.driver.AuthTokens;

import org.neo4j.driver.Driver;

import org.neo4j.driver.GraphDatabase;

public class DriverLifecycleExample implements AutoCloseable

{

Ê private final Driver driver;

Ê public DriverLifecycleExample( String uri, String user, String password )

Ê {

Ê driver = GraphDatabase.driver( uri, AuthTokens.basic( user, password ) );

Ê }

Ê @Override

Ê public void close() throws Exception

Ê {

Ê driver.close();

Ê }

}

Connection URIs

A connection URI identifies a graph database and how to connect to it.

The encryption and trust settings provide detail to how that connection should be secured.



There are significant changes to security settings between Neo4j 3.x and Neo4j 4.x

Please consider the information in this section before upgrading from a previous

version.

The Migration Guide is also a good source of information about changes in

functionality.

Starting with Neo4j 4.0, client-server communication uses only unencrypted local connections by

default.

This is a change from previous versions, which switched on encryption by default, but generated a

self-signed certificate out of the box.

When a full certificate is installed, and encryption is enabled on the driver, full certificate checks are

carried out (refer to Operations Manual → SSL framework). Full certificates provide better overall

security than self-signed certificates as they include a complete chain of trust back to a root certificate

authority.



Neo4j Aura is a secure hosted service backed by full certificates signed by a root

certificate authority.

To connect to Neo4j Aura, driver users must enable encryption and the complete set

of certificate checks (the latter of which are enabled by default).

For more information, see Examples below.

Table 2. Changes in default security settings between 3.x and 4.x

Setting Neo4j 4.x Neo4j 3.x (Drivers 1.x)

Bundled certificate none auto-generated, self-signed

Driver encryption off on

Bolt interface localhost localhost

Certificate expiry check on on

Certificate CA check on off

Certificate hostname check on off

Initial address resolution

The address provided in a neo4j:// URI is used for initial and fallback communication only.

This communication occurs to bootstrap the routing table, through which all subsequent

communication is carried out. Fallback occurs when the driver is unable to contact any of the

addresses held in the routing table. The initial address is once again reused to bootstrap the system.

Several options are available for providing this initial logical-to-physical host resolution. These include

regular DNS, custom middleware such as a load balancer, and the Driver Object resolver function, all of

which are described in the following sections.

DNS resolution

DNS resolution is the default, and always-available option. As it is possible to configure DNS to resolve

a single host name down to multiple IP addresses, this can be used to expose all core server IP

addresses under a single host name.

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