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事件驱动架构:从事件文档自动生成 DTO经过@dstepanov
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2,743 讀數

事件驱动架构:从事件文档自动生成 DTO

经过 Stepanov Dmitrii20m2022/09/22
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太長; 讀書

AsyncAPI 是一项开源计划,旨在改善事件驱动架构 (EDA) 的当前状态 AsyncApi 有多个工具可让您从代码生成文档。在本文中,我想告诉您我是如何解决以下任务的,即使用 springwolf 生成的 JSON 文档生成 DTO。
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在软件开发过程中,在项目的早期阶段经常被忽视的一件非常重要的事情是 API 文档。这个问题的解决方案之一是自动生成文档的框架。


在将项目划分为微服务并使用事件驱动架构的情况下,服务之间的交互是使用通过消息代理传输的事件来构建的。


要在事件驱动架构的情况下生成文档,有AsyncApi 。 AsyncAPI 是一项开源计划,旨在改善事件驱动架构 (EDA) 的当前状态。 AsyncApi 有几个 Java 工具,可让您从代码生成文档。在本文中,我描述了如何设置这些springwolf工具之一。


在本文中,我想告诉您我是如何解决以下任务的,即使用 springwolf 生成的 JSON 文档生成 DTO。

问题

spring wolf 生成的文档结构如下所示:


 { "service": { "serviceVersion": "2.0.0", "info": { //block with service info }, "servers": { "kafka": { //describe of kafka connection } }, "channels": { "kafka-channel": { "subscribe": { //... "message": { "oneOf": [ { "name": "pckg.test.TestEvent", "title": "TestEvent", "payload": { "$ref": "#/components/schemas/TestEvent" } } ] } }, //... } }, "components": { "schemas": { "TestEvent": { //jsonschema of component } } } } }


由于文档中使用 jsonschema 来描述组件,所以我决定使用jsonschema2pojo库来解决这个问题。然而,在尝试实施我的计划的过程中,我遇到了几个问题:


  • 您需要额外解析 JSON 文档以提取描述组件的对象。由于 jsonschema2pojo 将 jsonschema 对象作为输入,因此它们位于 components 块中。
  • jsonschema2pojo 不能很好地处理多态性,并且不能处理来自 AsyncAPI 中 oneOf 块的标准引用。继承的描述需要 schema 中的特殊字段(extends.javaType),不能简单的添加到 AsyncAPI 文档中。
  • 由于在我们的案例中生成的类应该用于反序列化来自代理的消息,因此有必要添加描述描述符和子类型的 Jackson 注释。


所有这些问题导致我需要在 jsonschema2pojo 上实现我的包装器,它将从文档中提取必要的信息,支持多态性,并添加 Jackson 注释。结果是一个 Gradle 插件,您可以通过它使用 springwolf API 为您的项目生成 DTO 类。接下来,我将尝试演示如何为文档类注解以及如何使用Springwolfdoc2dto插件。

文档设置

在这里,我想考虑一下非原始类型(如 Enum 和 Map)何时生成的细节。并且还描述了多态性的必要动作。


让我们看看下面的消息:


 @Getter @Setter @NoArgsConstructor @AllArgsConstructor public class TestEvent implements Serializable { private String id; private LocalDateTime occuredOn; private TestEvent.ValueType valueType; private Map<String, Boolean> flags; private String value; public enum ValueType { STRING("STRING"), BOOLEAN("BOOLEAN"), INTEGER("INTEGER"), DOUBLE("DOUBLE"); private final String value; public ValueType(String value) { this.value = value; } } }


此类消息的 jsonschema 如下所示:


 { "service": { //... "components": { "schemas": { "TestEvent": { "type": "object", "properties": { "id": { "type": "string", "exampleSetFlag": false }, "occuredOn": { "type": "string", "format": "date-time", "exampleSetFlag": false }, "valueType": { "type": "string", "exampleSetFlag": false, "enum": [ "STRING", "BOOLEAN", "INTEGER", "DOUBLE" ] }, "flags": { "type": "object", "additionalProperties": { "type": "boolean", "exampleSetFlag": false }, "exampleSetFlag": false }, "value": { "type": "string", "exampleSetFlag": false } }, "example": { "id": "string", "occuredOn": "2015-07-20T15:49:04", "valueType": "STRING", "flags": { "additionalProp1": true, "additionalProp2": true, "additionalProp3": true } }, "exampleSetFlag": true } } } } }


在生成 DTO 类时,我们会得到如下的类结构。您可以看到 Enum 的处理方式与原始版本一样,但是Map<String, Boolean>类型的集合已变成单独的类 Flags 并且集合本身的整个值将落入Flags.additionalProperties字段中。


 package pckg.test; // import @JsonInclude(JsonInclude.Include.NON_NULL) @JsonPropertyOrder({ "id", "occuredOn", "valueType", "flags", "value" }) @Generated("jsonschema2pojo") public class TestEvent implements Serializable { @JsonProperty("id") private String id; @JsonProperty("occuredOn") private LocalDateTime occuredOn; @JsonProperty("valueType") private TestEvent.ValueType valueType; @JsonProperty("flags") private Flags flags; @JsonProperty("value") private String value; @JsonIgnore private Map<String, Object> additionalProperties = new LinkedHashMap<String, Object>(); private final static long serialVersionUID = 7311052418845777748L; // Getters ans Setters @Generated("jsonschema2pojo") public enum ValueType { STRING("STRING"), BOOLEAN("BOOLEAN"), INTEGER("INTEGER"), DOUBLE("DOUBLE"); private final String value; private final static Map<String, TestEvent.ValueType> CONSTANTS = new HashMap<String, TestEvent.ValueType>(); static { for (TestEvent.ValueType c: values()) { CONSTANTS.put(c.value, c); } } ValueType(String value) { this.value = value; } @Override public String toString() { return this.value; } @JsonValue public String value() { return this.value; } @JsonCreator public static TestEvent.ValueType fromValue(String value) { TestEvent.ValueType constant = CONSTANTS.get(value); if (constant == null) { throw new IllegalArgumentException(value); } else { return constant; } } } } @JsonInclude(JsonInclude.Include.NON_NULL) @JsonPropertyOrder({ }) @Generated("jsonschema2pojo") public class Flags implements Serializable { @JsonIgnore private Map<String, Boolean> additionalProperties = new LinkedHashMap<String, Boolean>(); private final static long serialVersionUID = 7471055390730117740L; //getters and setters }

多态性

现在让我们看看如何提供多态性选项。当我们想要向一个代理主题发送多个消息子类型并为每个子类型实现我们的侦听器时,这是相关的。


为此,我们需要在提供者列表中添加一个父类,并将来自 swagger 的 @Schema 注解添加到它。


 @NoArgsConstructor(access = AccessLevel.PROTECTED) @AllArgsConstructor @Getter @Setter(AccessLevel.PROTECTED) @EqualsAndHashCode @JsonTypeInfo( use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "type", visible = true, defaultImpl = ChangedEvent.class ) @JsonSubTypes(value = { @JsonSubTypes.Type(name = ChangedEvent.type, value = ChangedEvent.class), @JsonSubTypes.Type(name = DeletedEvent.type, value = DeletedEvent.class) }) @JsonIgnoreProperties(ignoreUnknown = true) @Schema(oneOf = {ChangedEvent.class, DeletedEvent.class}, discriminatorProperty = "type", discriminatorMapping = { @DiscriminatorMapping(value = ChangedEvent.type, schema = ChangedEvent.class), @DiscriminatorMapping(value = DeletedEvent.type, schema = DeletedEvent.class), }) public abstract class DomainEvent { @Schema(required = true, nullable = false) private String id; @JsonSerialize(using = LocalDateTimeSerializer.class) @JsonDeserialize(using = LocalDateTimeDeserializer.class) @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd HH:mm:ss") private LocalDateTime occuredOn = LocalDateTime.now(); public abstract String getType(); } /** * Subtype ChangedEvent */ public class ChangedEvent extends DomainEvent implements Serializable { public static final String type = "CHANGED_EVENT"; private String valueId; private String value; } /** * Subtype DeletedEvent */ public class DeletedEvent extends DomainEvent implements Serializable { public static final String type = "DELETED_EVENT"; private String valueId; }


在这种情况下,文档中对组件的描述会发生如下变化:


 "components": { "schemas": { "ChangedEvent": { "type": "object", "properties": { "id": { "type": "string", "exampleSetFlag": false }, "occuredOn": { "type": "string", "format": "date-time", "exampleSetFlag": false }, "value": { "type": "string", "exampleSetFlag": false }, "valueId": { "type": "string", "exampleSetFlag": false }, "type": { "type": "string", "exampleSetFlag": false } }, "example": { "id": "string", "occuredOn": "2015-07-20T15:49:04", "value": "string", "valueId": "string", "type": "CHANGED_EVENT" }, "exampleSetFlag": true }, "DeletedEvent": { "type": "object", "properties": { "id": { "type": "string", "exampleSetFlag": false }, "occuredOn": { "type": "string", "format": "date-time", "exampleSetFlag": false }, "valueId": { "type": "string", "exampleSetFlag": false }, "type": { "type": "string", "exampleSetFlag": false } }, "example": { "id": "string", "occuredOn": "2015-07-20T15:49:04", "valueId": "string", "type": "DELETED_EVENT" }, "exampleSetFlag": true }, "DomainEvent": { "type": "object", "properties": { "id": { "type": "string", "exampleSetFlag": false }, "occuredOn": { "type": "string", "format": "date-time", "exampleSetFlag": false }, "type": { "type": "string", "exampleSetFlag": false } }, "example": { "id": "string", "occuredOn": "2015-07-20T15:49:04", "type": "string" }, "discriminator": { "propertyName": "type", "mapping": { "CHANGED_EVENT": "#/components/schemas/ChangedEvent", "DELETED_EVENT": "#/components/schemas/DeletedEvent" } }, "exampleSetFlag": true, "oneOf": [ { "$ref": "#/components/schemas/ChangedEvent", "exampleSetFlag": false }, { "$ref": "#/components/schemas/DeletedEvent", "exampleSetFlag": false } ] } } }


之后,插件将考虑来自 oneOf 块的链接和描述的鉴别器。结果,我们得到以下类结构。


 package pckg.test; // import @JsonInclude(JsonInclude.Include.NON_NULL) @JsonPropertyOrder({ "id", "occuredOn", "type" }) @Generated("jsonschema2pojo") @JsonTypeInfo(property = "type", use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, visible = true) @JsonSubTypes({ @JsonSubTypes.Type(name = "CHANGED_EVENT", value = ChangedEvent.class), @JsonSubTypes.Type(name = "DELETED_EVENT", value = DeletedEvent.class) }) public class DomainEvent implements Serializable { @JsonProperty("id") protected String id; @JsonProperty("occuredOn") protected LocalDateTime occuredOn; @JsonProperty("type") protected String type; @JsonIgnore protected Map<String, Object> additionalProperties = new LinkedHashMap<String, Object>(); protected final static long serialVersionUID = 4691666114019791903L; //getters and setters } // import @JsonInclude(JsonInclude.Include.NON_NULL) @JsonPropertyOrder({ "id", "occuredOn", "valueId", "type" }) @Generated("jsonschema2pojo") public class DeletedEvent extends DomainEvent implements Serializable { @JsonProperty("id") private String id; @JsonProperty("occuredOn") private LocalDateTime occuredOn; @JsonProperty("valueId") private String valueId; @JsonProperty("type") private String type; @JsonIgnore private Map<String, Object> additionalProperties = new LinkedHashMap<String, Object>(); private final static long serialVersionUID = 7326381459761013337L; // getters and setters } package pckg.test; //import @JsonInclude(JsonInclude.Include.NON_NULL) @JsonPropertyOrder({ "id", "occuredOn", "value", "type" }) @Generated("jsonschema2pojo") public class ChangedEvent extends DomainEvent implements Serializable { @JsonProperty("id") private String id; @JsonProperty("occuredOn") private LocalDateTime occuredOn; @JsonProperty("value") private String value; @JsonProperty("type") private String type; @JsonIgnore private Map<String, Object> additionalProperties = new LinkedHashMap<String, Object>(); private final static long serialVersionUID = 5446866391322866265L; //getters and setters }


插件设置

要连接插件,需要将其添加到 gradle.build 文件中并指定参数:

  • 文件夹用于生成 DTO

  • 新课程包

  • springwolf 文档 URL

  • 文档中的根名称,通常是服务的名称


plugins { id 'io.github.stepanovd.springwolf2dto' version '1.0.1-alpha' } springWolfDoc2DTO{ url = 'http://localhost:8080/springwolf/docs' targetPackage = 'example.package' documentationTitle = 'my-service' targetDirectory = project.layout.getBuildDirectory().dir("generated-sources") }


使用 bash 命令运行任务:


 ./gradle -q generateDTO

结论

在本文中,我描述了如何使用springwolfdocs2dto插件基于 AsyncApi 文档生成新的 DTO 类。同时,新的类将根据原始继承并包含杰克逊注释以进行正确的反序列化。我希望你发现这个插件对你有用。