在freemarker中,可以在包含文件之前检查文件是否存在吗?

时间:2010-04-13 15:38:44

标签: freemarker

我们正在尝试在freemarker中构建一个系统,可以选择添加扩展文件来替换标准模板的块。

我们已经到了这一点

<#attempt>
    <#include "extension.ftl">
<#recover>
    Standard output
</#attempt>

所以 - 如果extension.ftl文件存在,它将被使用,否则将输出recover块内的部分。

问题在于,freemarker始终记录导致恢复块触发的错误。

所以我们需要两件事之一:

  1. 如果文件不存在,请不要调用include - 因此需要检查文件是否存在。
  2. -OR -

    1. 一种防止在恢复块内记录错误而不更改日志记录以防止出现所有freemarker错误的方法。

5 个答案:

答案 0 :(得分:2)

更简单的解决方案是:

<#attempt>
    <#import xyz.ftl>
    your_code_here
<#recover>
</#attempt>

答案 1 :(得分:0)

我也有这个确切的需求,但我不想使用FreeMarker的ObjectConstructor(根据我的口味,它感觉太像一个小脚本)。

我写了一个自定义FileTemplateLoader

public class CustomFileTemplateLoader 
    extends FileTemplateLoader {

    private static final String STUB_FTL = "/tools/empty.ftl";

    public CustomFileTemplateLoader(File baseDir) throws IOException {
        super(baseDir);
    }


    @Override
    public Object findTemplateSource(String name) throws IOException {
        Object result = null;
        if (name.startsWith("optional:")) {
            result = super.findTemplateSource(name.replace("optional:", ""));
            if (result == null) {
                result = super.findTemplateSource(STUB_FTL);
            }
        }

        if (result == null) {
            result = super.findTemplateSource(name);
        }

        return result;
    }

}

我相应的FreeMarker宏:

<#macro optional_include name>
    <#include "/optional:" + name>
</#macro>

需要一个空的FTL文件(/tools/empty.ftl),该文件只包含解释其存在的注释。

结果是,如果找不到请求的FTL,“可选”包含将包含此空FTL。

答案 2 :(得分:0)

我们已经编写了一个自定义宏来解决这个问题。在早期测试中,它运作良好。要包含它,添加这样的东西(其中mm是Spring ModelMap):

mm.addAttribute(IncludeIfExistsMacro.MACRO_NAME, new IncludeIfExistsMacro());
import java.io.IOException;
import java.util.Map;

import org.apache.commons.io.FilenameUtils;

import freemarker.cache.TemplateCache;
import freemarker.cache.TemplateLoader;
import freemarker.core.Environment;
import freemarker.template.TemplateDirectiveBody;
import freemarker.template.TemplateDirectiveModel;
import freemarker.template.TemplateException;
import freemarker.template.TemplateModel;


/**
 * This macro optionally includes the template given by path.  If the template isn't found, it doesn't
 * throw an exception; instead it renders the nested content (if any).
 * 
 * For example: 
 * <@include_if_exists path="module/${behavior}.ftl">
 * <#include "default.ftl">
 * </@include_if_exists>
 * 
 * @param path the path of the template to be included if it exists
 * @param nested (optional) body could be include directive or any other block of code
 */
public class IncludeIfExistsMacro implements TemplateDirectiveModel {

    private static final String PATH_PARAM = "path";
    public static final String MACRO_NAME = "include_if_exists";

    @Override
    public void execute(Environment environment, Map map, TemplateModel[] templateModel,
            TemplateDirectiveBody directiveBody) throws TemplateException, IOException {

        if (! map.containsKey(PATH_PARAM)) {
            throw new RuntimeException("missing required parameter '" + PATH_PARAM + "' for macro " + MACRO_NAME);
        }

        // get the current template's parent directory to use when searching for relative paths
        final String currentTemplateName = environment.getTemplate().getName();
        final String currentTemplateDir = FilenameUtils.getPath(currentTemplateName);

        // look up the path relative to the current working directory (this also works for absolute paths)
        final String path = map.get(PATH_PARAM).toString();
        final String fullTemplatePath = TemplateCache.getFullTemplatePath(environment, currentTemplateDir, path);

        TemplateLoader templateLoader = environment.getConfiguration().getTemplateLoader();
        if (templateLoader.findTemplateSource(fullTemplatePath) != null) {
            // include the template for the path, if it's found
            environment.include(environment.getTemplateForInclusion(fullTemplatePath, null, true));
        } else {
            // otherwise render the nested content, if there is any
            if (directiveBody != null) {
                directiveBody.render(environment.getOut());
            }
        }
    }
}

答案 3 :(得分:0)

您也可以使用Java方法检查文件是否存在。

Java方法 -

public static boolean checkFileExistance(String filePath){
            File tmpDir = new File(filePath);
        boolean exists = tmpDir.exists();
        return exists;
    }

Freemarker Code -

<#assign fileExists = (Static["ClassName"].checkFileExistance("Filename"))?c/>
<#if fileExists = "true">
    <#include "/home/demo.ftl"/>
    <#else>
        <#include "/home/index.ftl">
</#if>

答案 4 :(得分:-1)

尝试此操作以获取基本路径:

<#assign objectConstructor = "freemarker.template.utility.ObjectConstructor"?new()>
<#assign file = objectConstructor("java.io.File","")>
<#assign path = file.getAbsolutePath()>
<script type="text/javascript">
alert("${path?string}");
</script>

然后这就走了目录结构:

<#assign objectConstructor = "freemarker.template.utility.ObjectConstructor"?new()>
<#assign file = objectConstructor("java.io.File","target/test.ftl")>
<#assign exist = file.exists()>
<script type="text/javascript">
alert("${exist?string}");
</script>