在 Spring Boot 使用 Freemarker 模板來快速建立客製化的標籤 (taglib) 是非常簡單的事. 作下列幾個步驟即可.

Step 01:  設定一個 Freemarker Template:  /src/main/resources/templates/demo/ftlTagSample.ftl

<body>    

    <div><h2>WELCOME,${userName}</h2></div>

    <div>Title:${userTitle}</div>

</body>

Step 02: 建立 tag 的 class : FtlTemplateTag.java

public class FtlTemplateTag extends TagSupport {

	private static final long serialVersionUID = 1L;
	
	private String fileName = null;
    private String paramsStr = null;
    private String columnsStr = null;
    private ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
    
	public void setFileName(String fileName) {
		this.fileName = fileName;
	}	   
	public void setParamsStr(String paramsStr) {
		this.paramsStr = paramsStr;
	}
	public void setColumnsStr(String columnsStr) {
		this.columnsStr = columnsStr;
	}
	/**
	 * JSON 字串轉換成 MAP
	 * @return
	 */
	private Map setParams() {
		Gson gson = new Gson();
		return gson.fromJson(paramsStr, new TypeToken>() {
		}.getType());
	}
	
	private Map setColumns(){
		Locale locale = LocaleContextHolder.getLocale();
		
		messageSource.setBasenames("i18n/messages");
		
		Gson gson = new Gson();
		Map columns = gson.fromJson(columnsStr, new TypeToken>() {}.getType() );
		
		//轉換多語系
		Map dataModel = new LinkedHashMap();
		columns.forEach( (k,v)-> dataModel.put(k, messageSource.getMessage(v, null, v, locale)) );
			
		return dataModel;
	}
	
	
	@Override
	public int doStartTag() throws JspException {
		JspWriter out = pageContext.getOut();
		
		Configuration conf = new Configuration();
		conf.setClassForTemplateLoading(this.getClass(), "/templates/");
		conf.setDefaultEncoding("UTF-8");
		
		try {
			Template  tl = conf.getTemplate(fileName);
			Map dataModel = new HashMap();
			dataModel.putAll(this.setParams());
			dataModel.put("columns", this.setColumns());
			

			tl.process(dataModel, out);
			
		} catch (Exception e) {
			e.printStackTrace();
		}		
		return Tag.SKIP_BODY;
	}
}

Step 03 建立標籤文件 tld:  /src/main/resources/static/tags/polinwei.tld

<?xml version="1.0" encoding="UTF-8" ?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
        version="2.0">
    <description>Polin WEI Tag Library</description>

    <tlib-version>1.0</tlib-version>
    <short-name>pw</short-name>
    <uri>/polinwei/tags</uri>

    <tag>
        <description>Get the file name of freemarker template</description>
        <name>FtlSampleTemplate</name>
        <tag-class>com.spring.jwt.tablibs.FtlTemplateTag</tag-class>
        <body-content>empty</body-content>
        <attribute>
            <description> Freemarker Template 的檔案</description>
            <name>fileName</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>parmsStr</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>columnsStr</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
</taglib>

Step 04: 註冊此 tag 

@Configuration
public class MvcConfig implements WebMvcConfigurer {
	 @Autowired
	 FreeMarkerConfigurer freeMarkerConfigurer;    
    /**
     *  
     *	  加入 spring-security-taglibs 對 FreeMarker 的支援
     */
    @PostConstruct    
    public void freeMarkerConfigurer() {
        List tlds = new ArrayList();        
        tlds.add("/static/tags/polinwei.tld");
        TaglibFactory taglibFactory = freeMarkerConfigurer.getTaglibFactory();
        taglibFactory.setClasspathTlds(tlds);
        if(taglibFactory.getObjectWrapper() == null) {
            taglibFactory.setObjectWrapper(freeMarkerConfigurer.getConfiguration().getObjectWrapper());
        }
    }

}

Step 05: 在 FTL or JSP 中使用

<p>測試從模版中讀取信息</p>
<@pw.FtlSampleTemplate fileName="demo/ftlTagSample.ftl" 
    paramsStr="{'Avatar':'polin.jpg','userName':'Polin WEI','userTitle':'MIS'}" />

 

Ref: https://blog.csdn.net/chinoukin/article/details/46683223

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