文件不存在时使用 #parse 的速度

发布于 2024-07-27 15:10:20 字数 309 浏览 8 评论 0原文

我们使用 Velocity 为几个不同的环境模板化我们的配置文件，这个过程运行得非常好，但我有一个关于解析不存在的文件的快速问题。

我的问题是：在解析文件之前如何检查文件是否存在？

因此，在示例中，文件 default.user.properties 可能合法地不存在，如果不存在，则不会解析文件的其余部分。

#parse("./default.user.properties")

我知道一种解决方案是确保文件始终存在，但如果我不需要这样做那就太好了。

提前致谢。

原文

we use Velocity to template our configuration files for several different environments and this process works really well but I have a quick question relating parsing a file that doesn't exist.

My question is:
How do you check if a file exists before parsing it?

So in the example the file default.user.properties might legitimately not exist and if it doesn't the rest of the file doesn't get parsed.

#parse("./default.user.properties")

I know one solution is to make sure the file is always there but it would be nice if I didn't have to.

Thanks in advance.

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忆梦 2024-08-03 15:10:20

只是用弹簧和速度做到了这一点：

我在获取速度来拾取事件处理程序时遇到问题，最后在 servlet xml 文件中指定它：

<bean id="velocityConfig" class="org.springframework.web.servlet.view.velocity.VelocityConfigurer">
        <property name="resourceLoaderPath" value="WEB-INF/templates"/>
        <property name="velocityPropertiesMap">
            <map>
                <entry key="eventhandler.include.class"><value>com.velocity.events.OptionalIncludeEventHandler</value></entry>
            </map>
        </property>
    </bean>

它根本不接受我将其放入属性文件中 - 它会实例化该类，但不将其注册为事件侦听器。非常令人沮丧。

该类本身很简单，是对现有速度类“org.apache.velocity.app.event.implementIncludeNotFound”的明显抄袭。现有的速度实现检查文件是否存在，如果不存在，则返回可配置的替代方案（默认值：notfound.vm）。

我的完全一样，只是如果文件不存在则返回 null，导致解析器跳过此包含/解析指令：

public class OptionalIncludeEventHandler implements IncludeEventHandler, RuntimeServicesAware {

    private RuntimeServices rs;

    @Override
    public void setRuntimeServices(RuntimeServices rs) {
        this.rs = rs;
    }

    @Override
    public String includeEvent(String includeResourcePath, String currentResourcePath, String directiveName) {
        return rs.getLoaderNameForResource(includeResourcePath) != null ? includeResourcePath : null;
    }

}

就像一个魅力一样。

希望它有用。

Just did this with spring and velocity:

I had problems getting velocity to pick up my event handler, in the end specifying it in the servlet xml file:

<bean id="velocityConfig" class="org.springframework.web.servlet.view.velocity.VelocityConfigurer">
        <property name="resourceLoaderPath" value="WEB-INF/templates"/>
        <property name="velocityPropertiesMap">
            <map>
                <entry key="eventhandler.include.class"><value>com.velocity.events.OptionalIncludeEventHandler</value></entry>
            </map>
        </property>
    </bean>

It simply would not accept me putting it in the properties file - it would instantiate the class, but not register it as an event listener. very frustrating.

The class itself is simple, a quite blatant rip off from the existing velocity class "org.apache.velocity.app.event.implementIncludeNotFound". The existing velocity implementation checks for the existance of the file, and if not present returns a configurable alternative (default: notfound.vm).

Mine is exactly the same except it returns null if the file does not exist, causing the parser to skip this include / parse directive:

public class OptionalIncludeEventHandler implements IncludeEventHandler, RuntimeServicesAware {

    private RuntimeServices rs;

    @Override
    public void setRuntimeServices(RuntimeServices rs) {
        this.rs = rs;
    }

    @Override
    public String includeEvent(String includeResourcePath, String currentResourcePath, String directiveName) {
        return rs.getLoaderNameForResource(includeResourcePath) != null ? includeResourcePath : null;
    }

}

Works like a charm.

Hope it's useful.

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潇烟暮雨 2024-08-03 15:10:20

一种新类型的事件处理程序“IncludeEventHandler”。这允许您（开发人员）定义一个类（实现 IncludeEventHandler），每次评估 #parse 或 #include 时都会调用该类。事件处理程序的目的是检查模板是否存在，如果不存在，则为调用代码设置错误标志。
尽管我自己没有测试过，但请查看文档以获取更多信息

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七色彩虹 2024-08-03 15:10:20

我使用的解决方案是创建一个实用方法来检查模板是否存在，即

public synchronized boolean templateExists(String templateFilename) {
    Boolean templateExists = this.templateExistsCache.get(templateFilename);
    if (templateExists != null) {
        return templateExists;
    }
    String absoluteFilename = this.request.getSession().getServletContext().getRealPath(
            "/WEB-INF/templates/" + templateFilename);
    File templateFile = new File(absoluteFilename);
    templateExists = templateFile.exists();
    this.templateExistsCache.put(templateFilename, templateExists);
    return templateExists;
}

private Map<String, Boolean> templateExistsCache = new HashMap<String, Boolean>();

来自

https://github.com/okohll/agileBase/blob/master/gtpb_server/src/com/gtwm/pb/model/manageData/ViewTools.java

The solution I used is to create a utility method for checking template existence, i.e.

public synchronized boolean templateExists(String templateFilename) {
    Boolean templateExists = this.templateExistsCache.get(templateFilename);
    if (templateExists != null) {
        return templateExists;
    }
    String absoluteFilename = this.request.getSession().getServletContext().getRealPath(
            "/WEB-INF/templates/" + templateFilename);
    File templateFile = new File(absoluteFilename);
    templateExists = templateFile.exists();
    this.templateExistsCache.put(templateFilename, templateExists);
    return templateExists;
}

private Map<String, Boolean> templateExistsCache = new HashMap<String, Boolean>();

from

https://github.com/okohll/agileBase/blob/master/gtpb_server/src/com/gtwm/pb/model/manageData/ViewTools.java

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