Freemarker:遍历 LinkedHashMap

Question

我有以下一段代码-

public class Result {
    private Map<String, String> dataPoints = new LinkedHashMap<String, String>();

    public Map<String, String> getData() {
        return Maps.newHashMap(data);
    }

    public Set<Map.Entry<String, String>> getDataEntries() {
        return data.entrySet();
    }

    public void addData(final String key, final String value) {
        this.data.put(key, value);
    }
}

我正在使用 LinkedHashMap，因为我想维护插入顺序。我正在尝试在我的 freemarker 代码中迭代 map ，如下所示。但是，我得到一个异常(exception)。

<#if (result.dataPoints?keys?size > 0) >
    <#list result.getDataEntries() as entry>
        <tr>
            <td width="35%">
                <div>${entry.key}</div>
            </td>
            <td width="45%">${entry.value}</td>
            <td width="19%">&nbsp;</td>
        </tr>
    </#list>
</#if>

异常(exception):

Expression result.getDataEntries is undefined on line 50, column 24 in settings/settings-
diagnostics.ftl. The problematic instruction: ---------- ==> list result.getDataEntries() 
as entry [on line 50, column 17 in settings/settings-diagnostics.ftl] in user-directive 
printDiagnosticResult [on line 64, column 25 in settings/settings-diagnostics.ftl] in 
user-directive printDiagnosticResult [on line 76, column 13 in settings/settings-
diagnostics.ftl] in user-directive layout.landingbase [on line 1, column 1 in     
settings/settings-diagnostics.ftl] ---------- Java backtrace for programmers: ---------- 
freemarker.core.InvalidReferenceException: Expression result.getDataEntries is undefined 
on line 50, column 24 in settings/settings-diagnostics.ftl. at 
freemarker.core.TemplateObject.assertNonNull(TemplateObject.java:124) at 
freemarker.core.TemplateObject.invalidTypeException(TemplateObject.java:134) at 
freemarker.core.MethodCall._getAsTemplateModel(MethodCall.java:114) at     
freemarker.core.Expression.getAsTemplateModel(Expression.java:89) at 
freemarker.core.IteratorBlock.accept(IteratorBlock.java:94) at     
freemarker.core.Environment.visit(Environment.java:208) at

如果我将上面的代码替换为:

<#if (result.dataPoints?keys?size > 0) >
    <#list result.dataPoints?keys as key>
        <tr>
            <td width="35%">
                <div>${key}</div>
            </td>
            <td width="45%">${result.dataPoints[key]}</td>
            <td width="19%">&nbsp;</td>
        </tr>
    </#list>
</#if>

知道如何遍历 map 以获得相同的顺序吗？

Answer 1

这应该可以解决问题:

<#if result.dataPoints?has_content >
    <#list result.dataPoints.entrySet() as entry>
        <tr>
            <td width="35%">
                <div>${entry.key}</div>
            </td>
            <td width="45%">${entry.value}</td>
            <td width="19%">&nbsp;</td>
        </tr>
    </#list>
</#if>

您可能还需要为 freemarker 模板配置设置对象包装器。像这样:

BeansWrapper beansWrapper = (BeansWrapper) ObjectWrapper.BEANS_WRAPPER;
beansWrapper.setExposeFields(true);
config.setObjectWrapper(beansWrapper);

其中 config 是 freemarker.template.Configuration。如果您使用 Spring Framework 然后扩展 FreeMarkerConfigurer:

public class FreeMarkerBeanWrapperConfigurer extends FreeMarkerConfigurer {
  @Override
  protected void postProcessConfiguration(Configuration config) throws IOException, TemplateException {
    super.postProcessConfiguration(config);

    BeansWrapper beansWrapper = (BeansWrapper) ObjectWrapper.BEANS_WRAPPER;
    beansWrapper.setExposeFields(true);
    config.setObjectWrapper(beansWrapper);
  }
}