SpringBoot+FreeMarker 学习（三）FreeMarker基本指令

短命女 2024-04-03 12:00 39阅读 0赞

FreeMarker的maven引用及application配置见第一篇教程

[SpringBoot+FreeMarker 学习（一）初识FreeMarker][SpringBoot_FreeMarker _FreeMarker]

## 一、if指令 ##

### <\#if condition> </\#if> ###

当condition值为false时，if标签内的东西会被忽略

例子：创建模板文件if.ftl

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Welcome!</title>
    </head>
    <body>
    <h1>Welcome ${user} <#if user == "Boss">, our boss</#if>!</h1>
    </body>
    </html>

创建LabelController

@Controller
    @RequestMapping(value = "label")
    public class LabelController {
    
        @RequestMapping("/if")
        public String ifLabel(String username, Model model) {
            model.addAttribute("user", username);
            return "if";
        }
    
    }

运行项目之后，分别访问

[http://127.0.0.1:8080/label/if?username=123][http_127.0.0.1_8080_label_if_username_123]

![62bb213336f04c2d809e8940f49384ff.png][]

[http://127.0.0.1:8080/label/if?username=Boss][http_127.0.0.1_8080_label_if_username_Boss]

![c285795f30724e3ea0cabad6e0c7c665.png][]

可以看到，输出的内容会根据 user == "Boss" 的判定条件做出改变。

### <\#else> <\#elseif condition> ###

else标签和elseif标签，可以让我们有更多的条件处理

例子：在上面if模板的基础上加上else判定语句

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Welcome!</title>
    </head>
    <body>
    <h1>Welcome ${user} <#if user == "Boss">, our boss</#if>!</h1>
    
    <h1>hello ${user} <#if user == "Boss">, our boss <#elseif user == "admin">, our admin <#else>, our ${user} </#if>!</h1>
    </body>
    </html>

LabelController不变，直接运行项目，分别访问三个地址，查看效果

[http://127.0.0.1:8080/label/if?username=123][http_127.0.0.1_8080_label_if_username_123]

![b2d62dc21b8e46e9b9d1e9a938eb4d82.png][]

[http://127.0.0.1:8080/label/if?username=admin][http_127.0.0.1_8080_label_if_username_admin]

![494f0ab45bd54bdc8dad76d31cfb1f63.png][]

[http://127.0.0.1:8080/label/if?username=Boss][http_127.0.0.1_8080_label_if_username_Boss]

![d8c15830c40542f4a276afe731c732e7.png][]

## 二、list指令 ##

### <\#list *sequence* as *loopVariable*>*repeatThis*</\#list> ###

list指令会遍历sequence数据，从第一项开始到最后一项，重复执行repeatThis代码。*loopVariable是sequence当前遍历项的值，仅在list标签内有效*

*例子：创建list.ftl模板*

<p>We have users:
    <table border=1>
        <#list users as user>
        <tr><td>${user.name}<td>${user.age}
        </#list>
    </table>

创建用户User实体类

@Getter
    @Setter
    public class User {
    
        private String name;
    
        private int age;
    
    }

在LabelController中添加

@RequestMapping("/list")
        public String listLabel(int userCount, Model model) {
            List<User> users = new ArrayList<>();
            for (int i = 0; i < userCount; i++) {
                User user = new User();
                user.setName(String.format("user%d", i + 1));
                user.setAge(i + 20);
                users.add(user);
            }
            model.addAttribute("users", users);
            return "list";
        }

运行项目之后访问地址： [http://127.0.0.1:8080/label/list?userCount=10][http_127.0.0.1_8080_label_list_userCount_10]

![634b7a4441e54cffa7435c0a6e30d534.png][]

### <\#items as *loopVariable*> *repeatThis* </\#items> ###

包含item标签之后，list指令将进行一个判定，看要遍历的列表是否为空，如果是空，则不执行，如果不为空，则在item标签内进行循环。

例子：在list.ftl模板的基础上，我们在加上一些代码

<p>We have users:
    <table border=1>
        <#list users as user>
        <tr><td>${user.name}<td>${user.age}
        </#list>
    </table>
    
    <br>
    
    <#list users>
        <table border=1>
            <#items as user>
            <tr><td>${user.name}<td>${user.age}
            </#items>
        </table>
    </#list>

分别访问 [http://127.0.0.1:8080/label/list?userCount=10][http_127.0.0.1_8080_label_list_userCount_10]

![f1cc6dda07bf4217b59aa15a1fb675ad.png][]

看展示效果没有区别，我们在访问 [http://127.0.0.1:8080/label/list?userCount=0][http_127.0.0.1_8080_label_list_userCount_0]

![6ed20682546d4ff9a044afc084677c69.png][]

两个table的展示效果，上面的生成了一个空的table，下面的写法没有生成table

查看网页源码更直观

![4a80d8130ff04bd39f45c29bdd19a0e7.png][]

### <\#sep> </\#sep> ###

sep指令在list中使用，只有当list中遍历的数据还有下一个时会执行里面的内容，否则忽略

例子：继续在list.ftl模板中添加代码

<p>We have users:
    <table border=1>
        <#list users as user>
        <tr><td>${user.name}<td>${user.age}<td> <#sep> have next</#sep>
        </#list>
    </table>
    
    <br>
    
    <#list users>
        <table border=1>
            <#items as user>
            <tr><td>${user.name}<td>${user.age}<td> <#sep> have next </#sep>
            </#items>
        </table>
    </#list>

访问地址：[http://127.0.0.1:8080/label/list?userCount=5][http_127.0.0.1_8080_label_list_userCount_5]

![5272e09a7b9a4ac58b2491c77de48b1a.png][]

### <\#else> ###

list标签可以和else同时使用，当list要遍历的数据为空时，执行else的代码

示例：在list.ftl模板中添加else代码

<p>We have users:
    <table border=1>
        <#list users as user>
        <tr><td>${user.name}<td>${user.age}<td> <#sep> have next</#sep>
        <#else>
        <tr><td>no user
        </#list>
    </table>
    
    <br>
    
    <#list users>
        <table border=1>
            <#items as user>
            <tr><td>${user.name}<td>${user.age}<td> <#sep> have next </#sep>
            </#items>
        </table>
    <#else>
        no one
    </#list>

访问地址： [http://127.0.0.1:8080/label/list?userCount=0][http_127.0.0.1_8080_label_list_userCount_0]

![36a2b64b412b43e985ad26db0e30fea1.png][]

## 三、include指令 ##

使用include指令可以在模板中插入其他文件的内容。

例子：我们创建一个copyright\_footer.html的文件

在创建一个模板文件include.ftl

LabelController中添加

@RequestMapping("/include")
        public String includeLabel(Model model) {
            return "include";
        }

运行项目之后访问地址： [http://127.0.0.1:8080/label/include][http_127.0.0.1_8080_label_include]

![cdb1f37b813746b19ad839991d3b47d6.png][]

测试代码地址： [HelloFreeMarker: SpringBoot+FreeMarker 学习][HelloFreeMarker_ SpringBoot_FreeMarker]

[SpringBoot_FreeMarker _FreeMarker]: https://blog.csdn.net/dengdaijc/article/details/127285221
[http_127.0.0.1_8080_label_if_username_123]: http://127.0.0.1:8080/label/if?username=123
[62bb213336f04c2d809e8940f49384ff.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/d5ab5b403d8e45e1ba4a76f2143920ce.png
[http_127.0.0.1_8080_label_if_username_Boss]: http://127.0.0.1:8080/label/if?username=Boss
[c285795f30724e3ea0cabad6e0c7c665.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/a101e5fd4b354cc89e394c2973a92f65.png
[b2d62dc21b8e46e9b9d1e9a938eb4d82.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/d0583af5f52a46ab885ab362eeb8ede5.png
[http_127.0.0.1_8080_label_if_username_admin]: http://127.0.0.1:8080/label/if?username=admin
[494f0ab45bd54bdc8dad76d31cfb1f63.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/96f893911dc44707968e294c008d2bcb.png
[d8c15830c40542f4a276afe731c732e7.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/e3bc14ea32014152bb8ba7d587a1296d.png
[http_127.0.0.1_8080_label_list_userCount_10]: http://127.0.0.1:8080/label/list?userCount=10
[634b7a4441e54cffa7435c0a6e30d534.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/1574a6e807e146d1a05f3ba0f12c70a1.png
[f1cc6dda07bf4217b59aa15a1fb675ad.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/fde3eeb338cb43f29dbb583899be9bff.png
[http_127.0.0.1_8080_label_list_userCount_0]: http://127.0.0.1:8080/label/list?userCount=0
[6ed20682546d4ff9a044afc084677c69.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/082861739ae44dbf9ec0be61e260cc12.png
[4a80d8130ff04bd39f45c29bdd19a0e7.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/606bf5599c974cee9cf9a7243e5f2b21.png
[http_127.0.0.1_8080_label_list_userCount_5]: http://127.0.0.1:8080/label/list?userCount=5
[5272e09a7b9a4ac58b2491c77de48b1a.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/2e8984c05fa24f38b9bf37c599ae671f.png
[36a2b64b412b43e985ad26db0e30fea1.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/726c0b741104486eb26a397fec59f4af.png
[http_127.0.0.1_8080_label_include]: http://127.0.0.1:8080/label/include
[cdb1f37b813746b19ad839991d3b47d6.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/88ceb9fdc964484fa6caf259088b2604.png
[HelloFreeMarker_ SpringBoot_FreeMarker]: https://gitee.com/xiaobailovejiajia/hello-free-marker