1.说明

ODL提供了Yang Tools工具从YANG文件生成Java类，
本文介绍使用Maven插件的方式生成，
基于yang-maven-plugin这个插件。

2.创建Maven工程

Eclipse -> File -> New -> Other... -> Maven -> Maven Project
创建一个简单Maven工程，
pom.xml如下：

<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.ai.prd.yang</groupId><artifactId>generate-yang-tools</artifactId><version>0.0.1-SNAPSHOT</version><description>使用ODL的Yang Tools工具，从yang文件生成Java类</description>
</project>

3.增加父pom

在pom.xml增加mdsal-parent作为父pom：

<parent><groupId>org.opendaylight.controller</groupId><artifactId>mdsal-parent</artifactId><version>1.10.4</version><relativePath>../../parent</relativePath>
</parent>

查看父pom，发现依赖了yang-maven-plugin插件：

<dependency><groupId>org.opendaylight.yangtools</groupId><artifactId>yang-maven-plugin</artifactId><version>3.0.16</version>
</dependency>

以及在build配置了这个插件从YANG生成Java类：

<plugin><groupId>org.opendaylight.yangtools</groupId><artifactId>yang-maven-plugin</artifactId><version>3.0.16</version><executions><execution><id>binding</id><goals><goal>generate-sources</goal></goals><configuration><codeGenerators><generator><codeGeneratorClass>org.opendaylight.mdsal.binding.maven.api.gen.plugin.CodeGeneratorImpl</codeGeneratorClass><outputBaseDir>D:\Code\Work\ODL-Netconf\yang-demos\generate-yang-tools\target-ide/generated-sources/mdsal-binding</outputBaseDir><resourceBaseDir>D:\Code\Work\ODL-Netconf\yang-demos\generate-yang-tools\target-ide/generated-sources/spi</resourceBaseDir></generator></codeGenerators><inspectDependencies>true</inspectDependencies></configuration></execution></executions><dependencies><dependency><groupId>org.opendaylight.mdsal</groupId><artifactId>maven-sal-api-gen-plugin</artifactId><version>2.0.17</version><scope>compile</scope></dependency></dependencies>
</plugin>

4.创建YANG文件

由于插件默认的YANG文件位置是src\main\yang，
所有在src\main\yang目录下新建文件acme-system.yang：

module acme-system {namespace "http://acme.example.com/system";prefix "acme";organization "ACME Inc.";contact "joe@acme.example.com";description"The module for entities implementing the ACME system.";revision 2007-06-09 {description "Initial revision.";}container system {leaf host-name {type string;description "Hostname for this system";}leaf-list domain-search {type string;description "List of domain names to search";}container login {leaf message {type string;description"Message given at start of login session";}list user {key "name";leaf name {type string;}leaf full-name {type string;}leaf class {type string;}}}}
}

对该YANG文件的解读请参考：对YANG的解读(一)

5.运行Maven插件

运行Maven命令，
执行插件功能,
从YANG文件生成Java类：

mvn clean generate-sources

Maven编译成功日志：

[INFO] Scanning for projects...
[INFO]
[INFO] ----------------< com.ai.prd.yang:generate-yang-tools >-----------------
[INFO] Building generate-yang-tools 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-clean-plugin:3.1.0:clean (default-clean) @ generate-yang-tools ---
[INFO]
[INFO] --- maven-enforcer-plugin:3.0.0-M2:enforce (enforce-maven) @ generate-yang-tools ---
[INFO]
[INFO] --- maven-enforcer-plugin:3.0.0-M2:enforce (enforce-banned-dependencies) @ generate-yang-tools ---
[INFO]
[INFO] --- git-commit-id-plugin:3.0.1:revision (get-git-infos) @ generate-yang-tools ---
[INFO]
[INFO] --- jacoco-maven-plugin:0.8.5:prepare-agent (pre-unit-test) @ generate-yang-tools ---
[INFO] argLine set to -javaagent:C:\\developtools\\maven-repository\\org\\jacoco\\org.jacoco.agent\\0.8.5\\org.jacoco.agent-0.8.5-runtime.jar=destfile=D:\\Code\\Work\\ODL-Netconf\\yang-demos\\generate-yang-tools\\target\\code-coverage\\jacoco.exec,excludes=**/gen/**:**/generated-sources/**:**/generated-test-sources/**:**/yang-gen/**:**/yang-gen-config/**:**/yang-gen-sal/**:**/yang-gen-code/**:**/pax/**
[INFO]
[INFO] --- yang-maven-plugin:3.0.16:generate-sources (binding) @ generate-yang-tools ---
[INFO] yang-to-sources: Code generator instantiated from org.opendaylight.mdsal.binding.maven.api.gen.plugin.CodeGeneratorImpl
[INFO] yang-to-sources: Inspecting D:\Code\Work\ODL-Netconf\yang-demos\generate-yang-tools\src\main\yang
[INFO] yang-to-sources: Found 0 dependencies in 40.39 ms
[INFO] yang-to-sources: Project model files found: 1
[INFO] yang-to-sources: 1 YANG models processed in 110.2 ms
[INFO] yang-to-sources: Sources will be generated to D:\Code\Work\ODL-Netconf\yang-demos\generate-yang-tools\target\generated-sources\mdsal-binding
[INFO] Found 5 Binding types in 58.11 ms
[INFO] Generating 8 Binding source files into 3 directories
[INFO] yang-to-sources: Sources generated by org.opendaylight.mdsal.binding.maven.api.gen.plugin.CodeGeneratorImpl: 11 in 136.5 ms
[INFO]
[INFO] --- build-helper-maven-plugin:3.0.0:add-source (add-yang-sources) @ generate-yang-tools ---
[INFO] Source directory: D:\Code\Work\ODL-Netconf\yang-demos\generate-yang-tools\target\generated-sources\mdsal-binding added.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  3.983 s
[INFO] Finished at: 2021-01-27T15:47:28+08:00
[INFO] ------------------------------------------------------------------------

6.查看生成的Java类

Maven命令执行成功后，
生成的Java类在工程的target\generated-sources\mdsal-binding目录下，
然后是Java类的包路径：org\opendaylight\yang\gen\v1\http\acme\example\com\system\rev070609，
目录rev070609的详细文件如下：

.:
system/  '$YangModelBindingProvider.java'  '$YangModuleInfoImpl.java'
AcmeSystemData.java  System.java  SystemBuilder.java./system:
login/  Login.java  LoginBuilder.java./system/login:
User.java  UserBuilder.java  UserKey.java

原始的YANG文件也会输出到target\generated-sources\yang\META-INF\yang下面，
并且重命名为acme-system@2007-06-09.yang。

由于生成的Java类都比较大，
这里仅贴出Login.java和LoginBuilder.java两个类。
Login.java:

package org.opendaylight.yang.gen.v1.http.acme.example.com.system.rev070609.system;
import java.lang.Class;
import java.lang.Override;
import java.lang.String;
import java.util.List;
import org.eclipse.jdt.annotation.NonNull;
import org.eclipse.jdt.annotation.Nullable;
import org.opendaylight.yang.gen.v1.http.acme.example.com.system.rev070609.$YangModuleInfoImpl;
import org.opendaylight.yang.gen.v1.http.acme.example.com.system.rev070609.System;
import org.opendaylight.yang.gen.v1.http.acme.example.com.system.rev070609.system.login.User;
import org.opendaylight.yangtools.yang.binding.Augmentable;
import org.opendaylight.yangtools.yang.binding.ChildOf;
import org.opendaylight.yangtools.yang.binding.CodeHelpers;
import org.opendaylight.yangtools.yang.common.QName;/*** * <p>* This class represents the following YANG schema fragment defined in module <b>acme-system</b>* <pre>* container login {*   leaf message {*     type string;*   }*   list user {*     key name;*     leaf name {*       type string;*     }*     leaf full-name {*       type string;*     }*     leaf class {*       type string;*     }*   }* }* </pre>The schema path to identify an instance is* <i>acme-system/system/login</i>* * <p>To create instances of this class use {@link LoginBuilder}.* @see LoginBuilder**/
public interface LoginextendsChildOf<System>,Augmentable<Login>
{public static final @NonNull QName QNAME = $YangModuleInfoImpl.qnameOf("login");@Overridedefault Class<org.opendaylight.yang.gen.v1.http.acme.example.com.system.rev070609.system.Login> implementedInterface() {return org.opendaylight.yang.gen.v1.http.acme.example.com.system.rev070609.system.Login.class;}/*** Message given at start of login session**** @return <code>java.lang.String</code> <code>message</code>, or <code>null</code> if not present*/@Nullable String getMessage();/*** @return <code>java.util.List</code> <code>user</code>, or <code>null</code> if not present*/@Nullable List<User> getUser();/*** @return <code>java.util.List</code> <code>user</code>, or an empty list if it is not present*/default @NonNull List<User> nonnullUser() {return CodeHelpers.nonnull(getUser());}
}

LoginBuilder.java:

package org.opendaylight.yang.gen.v1.http.acme.example.com.system.rev070609.system;
import com.google.common.base.MoreObjects;
import java.lang.Class;
import java.lang.Object;
import java.lang.Override;
import java.lang.String;
import java.lang.SuppressWarnings;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import org.opendaylight.yang.gen.v1.http.acme.example.com.system.rev070609.system.login.User;
import org.opendaylight.yangtools.concepts.Builder;
import org.opendaylight.yangtools.yang.binding.AbstractAugmentable;
import org.opendaylight.yangtools.yang.binding.Augmentation;
import org.opendaylight.yangtools.yang.binding.AugmentationHolder;
import org.opendaylight.yangtools.yang.binding.CodeHelpers;
import org.opendaylight.yangtools.yang.binding.DataObject;/*** Class that builds {@link LoginBuilder} instances. Overall design of the class is that of a* <a href="https://en.wikipedia.org/wiki/Fluent_interface">fluent interface</a>, where method chaining is used.* * <p>* In general, this class is supposed to be used like this template:* <pre>*   <code>*     LoginBuilder createTarget(int fooXyzzy, int barBaz) {*         return new LoginBuilderBuilder()*             .setFoo(new FooBuilder().setXyzzy(fooXyzzy).build())*             .setBar(new BarBuilder().setBaz(barBaz).build())*             .build();*     }*   </code>* </pre>* * <p>* This pattern is supported by the immutable nature of LoginBuilder, as instances can be freely passed around without* worrying about synchronization issues.* * <p>* As a side note: method chaining results in:* <ul>*   <li>very efficient Java bytecode, as the method invocation result, in this case the Builder reference, is*       on the stack, so further method invocations just need to fill method arguments for the next method*       invocation, which is terminated by {@link #build()}, which is then returned from the method</li>*   <li>better understanding by humans, as the scope of mutable state (the builder) is kept to a minimum and is*       very localized</li>*   <li>better optimization oportunities, as the object scope is minimized in terms of invocation (rather than*       method) stack, making <a href="https://en.wikipedia.org/wiki/Escape_analysis">escape analysis</a> a lot*       easier. Given enough compiler (JIT/AOT) prowess, the cost of th builder object can be completely*       eliminated</li>* </ul>* * @see LoginBuilder* @see Builder**/
public class LoginBuilder implements Builder<Login> {private String _message;private List<User> _user;Map<Class<? extends Augmentation<Login>>, Augmentation<Login>> augmentation = Collections.emptyMap();public LoginBuilder() {}public LoginBuilder(Login base) {if (base instanceof AugmentationHolder) {@SuppressWarnings("unchecked")Map<Class<? extends Augmentation<Login>>, Augmentation<Login>> aug =((AugmentationHolder<Login>) base).augmentations();if (!aug.isEmpty()) {this.augmentation = new HashMap<>(aug);}}this._message = base.getMessage();this._user = base.getUser();}public String getMessage() {return _message;}public List<User> getUser() {return _user;}@SuppressWarnings({ "unchecked", "checkstyle:methodTypeParameterName"})public <E$$ extends Augmentation<Login>> E$$ augmentation(Class<E$$> augmentationType) {return (E$$) augmentation.get(CodeHelpers.nonNullValue(augmentationType, "augmentationType"));}public LoginBuilder setMessage(final String value) {this._message = value;return this;}public LoginBuilder setUser(final List<User> values) {this._user = values;return this;}    public LoginBuilder addAugmentation(Class<? extends Augmentation<Login>> augmentationType, Augmentation<Login> augmentationValue) {if (augmentationValue == null) {return removeAugmentation(augmentationType);}if (!(this.augmentation instanceof HashMap)) {this.augmentation = new HashMap<>();}this.augmentation.put(augmentationType, augmentationValue);return this;}public LoginBuilder removeAugmentation(Class<? extends Augmentation<Login>> augmentationType) {if (this.augmentation instanceof HashMap) {this.augmentation.remove(augmentationType);}return this;}@Overridepublic Login build() {return new LoginImpl(this);}private static final class LoginImplextends AbstractAugmentable<Login>implements Login {private final String _message;private final List<User> _user;LoginImpl(LoginBuilder base) {super(base.augmentation);this._message = base.getMessage();this._user = base.getUser();}@Overridepublic String getMessage() {return _message;}@Overridepublic List<User> getUser() {return _user;}private int hash = 0;private volatile boolean hashValid = false;@Overridepublic int hashCode() {if (hashValid) {return hash;}final int prime = 31;int result = 1;result = prime * result + Objects.hashCode(_message);result = prime * result + Objects.hashCode(_user);result = prime * result + Objects.hashCode(augmentations());hash = result;hashValid = true;return result;}@Overridepublic boolean equals(Object obj) {if (this == obj) {return true;}if (!(obj instanceof DataObject)) {return false;}if (!Login.class.equals(((DataObject)obj).implementedInterface())) {return false;}Login other = (Login)obj;if (!Objects.equals(_message, other.getMessage())) {return false;}if (!Objects.equals(_user, other.getUser())) {return false;}if (getClass() == obj.getClass()) {// Simple case: we are comparing against selfLoginImpl otherImpl = (LoginImpl) obj;if (!Objects.equals(augmentations(), otherImpl.augmentations())) {return false;}} else {// Hard case: compare our augments with presence there...for (Map.Entry<Class<? extends Augmentation<Login>>, Augmentation<Login>> e : augmentations().entrySet()) {if (!e.getValue().equals(other.augmentation(e.getKey()))) {return false;}}// .. and give the other one the chance to do the sameif (!obj.equals(this)) {return false;}}return true;}@Overridepublic String toString() {final MoreObjects.ToStringHelper helper = MoreObjects.toStringHelper("Login");CodeHelpers.appendValue(helper, "_message", _message);CodeHelpers.appendValue(helper, "_user", _user);CodeHelpers.appendValue(helper, "augmentation", augmentations().values());return helper.toString();}}
}

7.问题解决

在Eclipse缺少某些插件时，
会报Maven的一些goals无法执行的错误，
下面配置去掉Eclipse中的pom报错，
并且不影响Maven命令执行结果:

<build><pluginManagement><plugins><!--This plugin's configuration is used to store Eclipse m2e settings only. It has no influence on the Maven build itself.--><plugin><groupId>org.eclipse.m2e</groupId><artifactId>lifecycle-mapping</artifactId><version>1.0.0</version><configuration><lifecycleMappingMetadata><pluginExecutions><pluginExecution><pluginExecutionFilter><groupId>com.github.spotbugs</groupId><artifactId>spotbugs-maven-plugin</artifactId><versionRange>[3.1.12.2,)</versionRange><goals><goal>check</goal></goals></pluginExecutionFilter><action><ignore></ignore></action></pluginExecution><pluginExecution><pluginExecutionFilter><groupId>org.apache.maven.plugins</groupId><artifactId>maven-checkstyle-plugin</artifactId><versionRange>[3.1.1,)</versionRange><goals><goal>check</goal></goals></pluginExecutionFilter><action><ignore></ignore></action></pluginExecution></pluginExecutions></lifecycleMappingMetadata></configuration></plugin></plugins></pluginManagement>
</build>

8.使用ODL提供的样例工程

ODL提供了一个和上面类似的工程，
下载地址：https://github.com/opendaylight/controller/releases?after=v2.0.5
选择下载版本release/sodium-sr4，
这个是钠版本的稳定发布版本，
且支持JDK 1.8和Maven 3.6.9，
这是由于在父pom中指定了requireJavaVersion为1.8.0，
以及requireMavenVersion大于等于3.5.0。

<plugin><artifactId>maven-enforcer-plugin</artifactId><version>3.0.0-M2</version><executions><execution><id>enforce-maven</id><goals><goal>enforce</goal></goals><configuration><rules><requireJavaVersion><version>1.8.0</version></requireJavaVersion><requireMavenVersion><version>[3.5.0,)</version></requireMavenVersion></rules></configuration></execution><execution><id>enforce-banned-dependencies</id><goals><goal>enforce</goal></goals><configuration><rules><bannedDependencies><message>Please always use mockito-core instead of mockito-all (see https://bugs.opendaylight.org/show_bug.cgi?id=7662), and spotbugs:annotations instead of findbugs:annotations</message><excludes><exclude>org.mockito:mockito-all</exclude><exclude>com.google.code.findbugs:annotations</exclude></excludes></bannedDependencies></rules><fail>true</fail></configuration></execution></executions>
</plugin>

9.使用样例工程

下载的controller-release-sodium-sr4.zip解压到本地，
找到toaster工程：
D:\temp\controller-release-sodium-sr4\opendaylight\md-sal\samples\toaster
然后在工程下面执行编译命令即可:

mvn clean generate-sources

也可以把工程复制出来单独编译，
也可以把工程导入Eclipse编译，
生成的结果和上面类似。

10.参考文章

使用yangtools将yang文件转化成javaYang Tools Github