在 Eclipse 中从 XML 生成 Java 代码

Question

我正在开发一个项目，该项目将包含几个彼此非常相似的 Java 类，并且我想从 XML 文件生成这些类。我希望能够做的是改变 Eclipse 构建过程来做这样的事情：

• 编译代码生成器
• 运行代码生成器，将 XML 转换为 Java
• 编译项目的其余部分

我可以手动完成这一切，但我更愿意让 Eclipse 为我完成这一切。

例子

我希望能够采用如下所示的源 XML 文件：

<command-list>
    <command name="DATE" />
    <command name="GROUP">
        <capability "READER" />
        <argument "groupname" />
    </command>
    <command name="ARTICLE">
        <capability "READER" />
        <argument "message-id" optional="true" />
    </command>
</command-list>

并让它给我类似于以下内容（在适当的单独文件中）：

public class Date extends Command {
    public ResponseCode execute() {
        Server srv = getServer();
        srv.send("DATE");
        return srv.getResponse();
    }
}

public class Group extends Command {
    public ResponseCode execute() {
        Server srv = getServer();
        if (srv.hasCapability(Capabilities.READER) == false) {
            Log.debug("Attempting non-available capability: READER");
        }
        String groupname = getArgument("groupname");
        if (groupname == null) {
             throw new InvalidArgumentException("Require groupname");
        }
        String command = "GROUP";
        if (groupname != null) command += " " + groupname;
        srv.send(command);
        return srv.getResponse();
    }
}

public class Article extends Command {
    public ResponseCode execute() {
        Server srv = getServer();
        if (srv.hasCapability(Capabilities.READER) == false) {
            Log.debug("Attempting non-available capability: READER");
        }
        String messageId = getArgument("messageId");
        String command = "ARTICLE";
        if (messageId != null) command += " " + messageId;
        srv.send(command);
        return srv.getResponse();
    }
}

Answer 1

这正是模型到文本 (M2T) 项目中的 JET 组件的用途。事实上，您甚至可以使用 JET 创建项目、.classpath 和任何其他您需要的文件。

Jet 模板如下。请注意，这些模板的命名必须与所示的完全一致。

/模板/main.jet

<%@taglib prefix="ws" id="org.eclipse.jet.workspaceTags" %>
<%-- Main entry point for com.lacqui.command.xform --%>

<%-- 
  Let c:iterate tags set the XPath context object.
  For 100% compatibility with JET 0.9.x or earlier, remove this statement
 --%>
<c:setVariable var="org.eclipse.jet.taglib.control.iterateSetsContext" select="true()"/>

    <c:setVariable select="/command-list" var="command-list" />

    --- traverse input model, performing calculations and storing 
    --- the results as model annotations via c:set tag 

    <c:set select="$command-list" name="project">com.lacqui.commands</c:set>
    <c:set select="$command-list" name="commandPkg">com.lacqui.commands</c:set>
    <c:set select="$command-list" name="commandDir"><c:get select="translate($command-list/@commandPkg,'.','/')" /></c:set>

    <c:iterate select="$command-list/command" var="command" >

            - Derive the class name from the name of the command

        <c:set select="$command" name="classname"><c:get select="camelCase($command/@name)" />Command</c:set>

        <c:iterate select="$command/argument" var="argument">

            <c:if test="not($argument/@optional)">
                <c:set select="$argument" name="optional">false</c:set>
            </c:if>

        </c:iterate>

    </c:iterate>

   --- traverse annotated model, performing text generation actions 
   --- such as ws:file, ws:folder and ws:project 

   <ws:project name="{$command-list/@project}" />
   <ws:file template="templates/project.jet" path="{$command-list/@project}/.project"  />
   <ws:file template="templates/classpath.jet" path="{$command-list/@project}/.classpath"/>

    <c:iterate select="$command-list/command" var="command" >

        <ws:file template="templates/class.jet" path="{$command-list/@project}/src/{$command-list/@commandDir}/{$command/@classname}.java" replace="true"/>

    </c:iterate>

/templates/classpath.jet

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
    <classpathentry kind="src" path="src"/>
    <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
    <classpathentry kind="output" path="bin"/>
</classpath>

/模板/project.jet

<?xml version="1.0" encoding="UTF-8"?>
<projectDescription>
    <name><c:get select="$command-list/@project" /></name>
    <comment></comment>
    <projects>
    </projects>
    <buildSpec>
        <buildCommand>
            <name>org.eclipse.jdt.core.javabuilder</name>
            <arguments>
            </arguments>
        </buildCommand>
    </buildSpec>
    <natures>
        <nature>org.eclipse.jdt.core.javanature</nature>
    </natures>
</projectDescription>

/模板/class.jet

package <c:get select="$command-list/@commandPkg" />;

public class <c:get select="$command/@classname" /> extends Command {
    public ResponseCode execute() {
        Server srv = getServer();
<c:iterate select="$command/capability" var="capability">

        if (srv.hasCapability(Capabilities.<c:get select="$capability/@name"/>) == false) {
            Log.debug("Attempting non-available capability: <c:get select="$capability/@name"/>");
        }
</c:iterate>        
<c:iterate select="$command/argument" var="argument">

        String <c:get select="$argument/@name"/> = getArgument("<c:get select="$argument/@name"/>");
<c:if test="$argument/@optional = 'false'" >
        if (<c:get select="$argument/@name"/> == null) {
             throw new InvalidArgumentException("Require <c:get select="$argument/@name"/>");
        }
</c:if>
</c:iterate>        

        String command = "GROUP";
<c:iterate select="$command/argument" var="argument">
        if (<c:get select="$argument/@name"/> != null) command += " -<c:get select="$argument/@name"/> " + <c:get select="$argument/@name"/>;
</c:iterate>       

        srv.send(command);
        return srv.getResponse();
    }
}

并使用这个模型：

<command-list>
    <command name="DATE" />
    <command name="GROUP">
        <capability name="LOGGER" />
        <capability name="AUTHENTICATOR" />
        <argument name="groupname" />
    </command>
    <command name="ARTICLE">
        <capability name="READER" />
        <argument name="article-id" optional="false" />
        <argument name="message-id" optional="true" />
    </command>
</command-list>

给出了一个名为 com.lacqui.commands 的完整 java 项目，其中包含三个 java 文件：

package com.lacqui.commands;

public class ArticleCommand extends Command {
    public ResponseCode execute() {
        Server srv = getServer();

        if (srv.hasCapability(Capabilities.READER) == false) {
            Log.debug("Attempting non-available capability: READER");
        }

        String article-id = getArgument("article-id");
        if (article-id == null) {
             throw new InvalidArgumentException("Require article-id");
        }

        String message-id = getArgument("message-id");

        String command = "GROUP";
        if (article-id != null) command += " -article-id " + article-id;
        if (message-id != null) command += " -message-id " + message-id;

        srv.send(command);
        return srv.getResponse();
    }
}

和这个：

package com.lacqui.commands;

public class GroupCommand extends Command {
    public ResponseCode execute() {
        Server srv = getServer();

        if (srv.hasCapability(Capabilities.LOGGER) == false) {
            Log.debug("Attempting non-available capability: LOGGER");
        }

        if (srv.hasCapability(Capabilities.AUTHENTICATOR) == false) {
            Log.debug("Attempting non-available capability: AUTHENTICATOR");
        }

        String groupname = getArgument("groupname");
        if (groupname == null) {
             throw new InvalidArgumentException("Require groupname");
        }

        String command = "GROUP";
        if (groupname != null) command += " -groupname " + groupname;

        srv.send(command);
        return srv.getResponse();
    }
}