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模板引擎Velocity学习系列 - #set指令

#set指令

#set指令用于向一个变量或者对象赋值。

格式: #set($var = value)

LHS是一个变量,不要使用特殊字符例如英文句号等,不能用大括号括起来。测试发现#set($user.name = 'zhangsan'),#set(${age} = 18)均赋值失败。

RHS可以是变量、字符串字面值、数字字面值、方法、ArrayList、Map、表达式。

测试案例

User对象类

public class User {

    private String name;
    private int age;
    
    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

}

测试类TestVelocity

public class TestVelocity {

    public static void main(String[] args) {
        
        VelocityEngine engine = new VelocityEngine();
        // 初始化VelocityEngine
        engine.setProperty("resource.loader", "file");
        engine.setProperty("file.resource.loader.class",
                "org.apache.velocity.runtime.resource.loader.FileResourceLoader");
        engine.setProperty("input.encoding", "utf8");
        engine.setProperty("output.encoding", "utf8");
        engine.setProperty(VelocityEngine.FILE_RESOURCE_LOADER_PATH, "D://conf");
        engine.init();

        Template template = engine.getTemplate("hellovelocity.vm");

        VelocityContext ctx = new VelocityContext();
        ctx.put("user", new User("zhangsan", 18));

        StringWriter stringWriter = new StringWriter();
        template.merge(ctx, stringWriter);
        System.out.println(stringWriter.toString());
    }
    
}

测试模板文件 hellovelocity.vm

#set($name = 'john')
#set($age = 18)
#set($array = ['a', 'b', 'c'])
#set($map = {'a' : 'a', 'b' : 'b', 'c' : 'c'})
#set($userName = "$!{user.getName()}")
#set($userAge = "$!{user.getAge()}")
#set($userTest1 = $user.getAge_())
#set($userTest2 = "$!{user.getAge_()}")


$name  $age  $array.get(0) $array.get(1) $array.get(2) $map.get('a') $map.get('b') $map.get('c')
$userName $userAge $userTest1 $userTest2

输出结果


john  18  a b c a b c
zhangsan 18 $userTest1

说明:

#set($userTest1 = $user.getAge_())

#set($userTest2 = "$!{user.getAge_()}")

右边$!{user.getAge_()}表达式计算失败情况下,放在双引号里面,赋值空串,放在外面将不会赋值。

在使用#set时,字符串的字面值如果放在双引号里,将会被解析,放在单引号里面,将会被当做字面量。

#set($test1 = "$userName")

#set($test2 = '$userName')

$test1=字符串zhangsan,$test2=字符串$userName。
原文  http://www.cnblogs.com/red-bull/p/11564109.html
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