Handlebars.java 没有很好的文档记录并且缺少几个单元测试(如果这个答案有帮助,请考虑贡献),由于某种原因,在此JsonObject
提交中调用 nested删除,您仍然可以调用 nested ,但有一个带括号的技巧。String
完整示例:
import com.github.jknack.handlebars.Context;
import com.github.jknack.handlebars.Handlebars;
import com.github.jknack.handlebars.Helper;
import com.github.jknack.handlebars.Template;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import java.io.IOException;
import java.lang.reflect.Type;
import java.util.Map;
public class HandlebarsJavaTest {
public static void main(String[] args) throws IOException {
Handlebars handlebars = new Handlebars();
Gson gson = new Gson();
handlebars.registerHelper("getLink", (Helper<Map<String, Object>>) (jsonObject, options) -> {
String link = fetchLink(jsonObject);
return link != null ? link : "";
});
String data = "{'data':{'node':'/bla.html', 'node2':'inside node2'}}";
// Pay attention to parentheses !!!
// {{#if (getLink data.node)}} throws ClassCastException, java.lang.String cannot be cast to java.util.Map
String rawTemplate = "{{#if (getLink data)}} <a href=\"{{getLink data}}\">Link-Text</a> {{/if}}";
Type type = new TypeToken<Map<String, Object>>(){}.getType();
Map<String, Object> map = gson.fromJson(data, type);
Template template = handlebars.compileInline(rawTemplate);
Context context = Context.newBuilder(map).build();
System.out.println(template.apply(context));
}
private static String fetchLink(Map<String, Object> map) {
try {
return map.get("node").toString();
} catch (NullPointerException npe) {
return null;
}
}
}
输出:
<a href="/bla.html">Link-Text</a>
如果节点只是一个字符串(相同的输出)
public static void main(String[] args) throws IOException {
Handlebars handlebars = new Handlebars();
Gson gson = new Gson();
handlebars.registerHelper("getLink", (Helper<String>) (node, options) -> node != null ? node : "");
String data = "{'data':{'node':'/bla.html', 'node2':'inside node2'}}";
// Pay attention to parentheses !!!
String rawTemplate = "{{#if (getLink data.node)}} <a href=\"{{getLink data.node}}\">Link-Text</a> {{/if}}";
Type type = new TypeToken<Map<String, Object>>(){}.getType();
Map<String, Object> map = gson.fromJson(data, type);
Template template = handlebars.compileInline(rawTemplate);
Context context = Context.newBuilder(map).build();
System.out.println(template.apply(context));
}
如果您坚持 node 是一个使用this.[data]
或this.[data.node]
不会执行工作的对象,则相同输出的工作示例:
import com.github.jknack.handlebars.Context;
import com.github.jknack.handlebars.Handlebars;
import com.github.jknack.handlebars.Helper;
import com.google.gson.Gson;
import com.google.gson.JsonObject;
public class HandlebarsJavaTest {
public static void main(String[] args) throws Exception {
System.out.println(
new Handlebars()
.registerHelper("getLink", (Helper<JsonObject>) (json, options) -> {
try {
// logic here
return json.get("data").getAsJsonObject().get("node").getAsJsonObject().get("link").getAsString();
} catch (NullPointerException npe) {
return null;
}
})
// Pay attention to parentheses !!
.compileInline("{{#if (getLink this) }} <a href=\"{{getLink this}}\">Link-Text</a> {{/if}}")
.apply(
Context
.newBuilder(
new Gson()
.fromJson(
"{ 'data': { 'node': { 'link': '/bla.html' }, 'node2': 'inside node2' } }",
JsonObject.class
)
).build()
)
);
}
}
如果您有时间,请考虑通过添加适当的文档或至少单元测试来为这个开源做出贡献{{#if (method param)}}
。
根据源代码
package com.github.jknack.handlebars;
public class IfBlockTest extends AbstractTest {
@Test
public void falsy() throws IOException {
// empty string
shouldCompileTo("{{#if value}}true{{else}}false{{/if}}", $("value", ""), "false");
顺便说一句,#if
内置帮助程序将返回False
空字符串,因此 ifgetLink
将不会执行return "";
if 条件并且不会呈现文本,要断言这一点,您可以{{else}}
在关闭 if 之前添加{{/if}}
并查看呈现的内容。