在Eclipse中從XML生成Java代碼

Question

我正在研究一個項目，該項目將具有多個彼此非常類似的Java類，並且我希望從XML文件生成這些類。我希望能夠做的是改變Eclipse構建過程中做這樣的事情：

• 編譯代碼生成器
• 運行代碼生成器，將XML轉換成Java
• 編譯休息的項目

我可以手動完成這一切，但我更希望能夠讓Eclipse爲我做這一切。

例

我希望能夠把看起來像這樣的一個源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> 

，並把它給了我類似下面的內容（在單獨的文件作爲適當的）：

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

這正是模型到文本（M2T）項目中的JET組件所做的。實際上，您甚至可以使用JET創建項目，.classpath和任何其他需要的文件。

Jet模板如下。請注意，這些模板必須完全按照所示進行命名。

/templates/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> 

/templates/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> 

/templates/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(); 
    } 
} 

，並利用該模型：

<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> 

給人命名包含三個Java文件com.lacqui.commands一個完整的Java項目：

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(); 
    } 
} 

這：

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(); 
    } 
} 

Answer 2

你可能想看看JaxB。

拉爾斯沃格爾做了一個簡單的教程，如果你想快速瀏覽它。
JAXB Tutorial

另外這裏是xml unmarshaling的基準測試。
XML unmarshalling benchmark in Java: JAXB vs STax vs Woodstox

Answer 3

您要使用的是您的項目屬性中的「Builders」選項。在這裏，您可以設置您的項目，在編譯其餘項目之前，使用'ant'腳本編譯和執行代碼生成器（其他類型的構建器也可用）。

我認爲這些文章更好的解釋：

http://www.eclipsezone.com/eclipse/forums/t65486.html

http://help.eclipse.org/juno/index.jsp?topic=%2Forg.eclipse.platform.doc.user%2FgettingStarted%2Fqs-93_project_builder.htm