FreeMarker — Java 模版引擎 (2) – APPX Tech 時賦科技 Blog

關於樣版的制定，FreeMarker提供了相當多的支援，如果已經熟悉JSP taglib, expression language (EL)的同學來學習 FreeMarker 樣版，會發現語法還蠻類似的，很容易就可以上手！以下提供幾個常用的特性，完整說明，可參考官方文件。

我們先修改一下範例程式

新增Book.java

package com.appx.demo.freemarker;

public class Book {
    private String name;
    private String author;

    public Book(String name, String author) {
        this.name = name;
        this.author = author;
    }

    //getter, setter 請自行補上...
}

package com.appx.demo.freemarker;

public class Book {

private String name;

private String author;

public Book(String name, String author) {

this.name = name;

this.author = author;

}

//getter, setter 請自行補上...

}

修改User.java

package com.appx.demo.freemarker;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;

public class User {
    private String name;
    private String location;
    private int cash;
    private Date createdDate;
    private List<Book> books = new ArrayList<>();

    public User(String name, String location, int cash, Date createdDate) {
        this.name = name;
        this.location = location;
        this.cash = cash;
        this.createdDate = createdDate;
    }

    public void addBook(Book book) {
        this.books.add(book);
    }

    // getter, setter 請自行補上...
}

package com.appx.demo.freemarker;

import java.util.ArrayList;

import java.util.Date;

import java.util.List;

public class User {

private String name;

private String location;

private int cash;

private Date createdDate;

private List<Book> books = new ArrayList<>();

public User(String name, String location, int cash, Date createdDate) {

this.name = name;

this.location = location;

this.cash = cash;

this.createdDate = createdDate;

}

public void addBook(Book book) {

this.books.add(book);

}

// getter, setter 請自行補上...

}

稍微重構一下主程式App.java

package com.appx.demo.freemarker;

import java.io.StringWriter;
import java.util.Date;

import freemarker.template.Configuration;

public class App {

    public static void main(String[] args) throws Exception {        
        //初始化freemarker設定
        Configuration cfg = new Configuration(Configuration.VERSION_2_3_26);
        //指定樣版所在位置 (這裡是classpath的templates資料夾底下)
        cfg.setClassForTemplateLoading(App.class, "/templates");
        cfg.setDefaultEncoding("UTF-8");

        //封裝資料的物件，可以是一般物件，也可以是List, Map 等集合物件
        User user = prepareData();

        //取得樣版處理後輸出到 StringWriter
        StringWriter sw = new StringWriter();
        cfg.getTemplate("helloworld.ftl").process(user, sw);

        //透過StringWriter的toString()取得內容，後續可以進行處理
        System.out.println(sw);
    }

    private static User prepareData() {
        User user = new User("Terry", "Taiwan", 201234, new Date());
        user.addBook(new Book("Java in Action", "Anderson"));
        user.addBook(new Book("Oracle tutorial", "Tom"));
        return user;
    }
}

package com.appx.demo.freemarker;

import java.io.StringWriter;

import java.util.Date;

import freemarker.template.Configuration;

public class App {

public static void main(String[] args) throws Exception {

//初始化freemarker設定

Configuration cfg = new Configuration(Configuration.VERSION_2_3_26);

//指定樣版所在位置 (這裡是classpath的templates資料夾底下)

cfg.setClassForTemplateLoading(App.class, "/templates");

cfg.setDefaultEncoding("UTF-8");

//封裝資料的物件，可以是一般物件，也可以是List, Map 等集合物件

User user = prepareData();

//取得樣版處理後輸出到 StringWriter

StringWriter sw = new StringWriter();

cfg.getTemplate("helloworld.ftl").process(user, sw);

//透過StringWriter的toString()取得內容，後續可以進行處理

System.out.println(sw);

}

private static User prepareData() {

User user = new User("Terry", "Taiwan", 201234, new Date());

user.addBook(new Book("Java in Action", "Anderson"));

user.addBook(new Book("Oracle tutorial", "Tom"));

return user;

}

修改helloworld.ftl，請留意Freemarker 註解中各項說明

<html>
<header></header>
<body>
    <h1>Hello, ${name}!</h1>

    <#-- 多層資料結構 -->
    The first book: ${books[0].name}

    <#-- 字串處理 -->    
    User location: ${location?upper_case}

    <#-- 數字格式化 -->
    Cash: ${cash?string.currency}

    <#-- 日期格式化 -->
    Created Date: ${createdDate?string["yyyy-MM-dd"]}

    <#-- if else 邏輯處理 -->
    <#if (cash > 100000)>
    Rich
    <#else>
    Make more money
    </#if>
    
    <#-- for迴圈取出資料 -->
    <#list books as book>
    ${book?counter}: ${book.name}, written by ${book.author}
    </#list>
</body>
<#-- 匯入其它樣版內容 -->
<#include "footer.ftl">
</html>

<html>

<body>

<h1>Hello, ${name}!</h1>

<#-- 多層資料結構 -->

The first book: ${books[0].name}

<#-- 字串處理 -->

User location: ${location?upper_case}

<#-- 數字格式化 -->

Cash: ${cash?string.currency}

<#-- 日期格式化 -->

Created Date: ${createdDate?string["yyyy-MM-dd"]}

<#-- if else 邏輯處理 -->

<#if (cash > 100000)>

Rich

<#else>

Make more money

</#if>

<#-- for迴圈取出資料 -->

<#list books as book>

${book?counter}: ${book.name}, written by ${book.author}

</#list>

</body>

<#-- 匯入其它樣版內容 -->

<#include "footer.ftl">

</html>

新增 footer.ftl

XHTML

${.now?string["yyyy"]} Appx rocks!

1

${.now?string["yyyy"]} Appx rocks!

執行結果

<html>
<header></header>
<body>
    <h1>Hello, Terry!</h1>

    The first book: Java in Action

    User location: TAIWAN

    Cash: $201,234.00

    Created Date: 2017-05-11

    Rich
    
    1: Java in Action, written by Anderson
    2: Oracle tutorial, written by Tom
</body>
2017 Appx rocks!
</html>

<html>

<body>

<h1>Hello, Terry!</h1>

The first book: Java in Action

User location: TAIWAN

Cash: $201,234.00

Created Date: 2017-05-11

Rich

1: Java in Action, written by Anderson

2: Oracle tutorial, written by Tom

</body>

2017 Appx rocks!

</html>

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