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I have some issues overriding default configuration of Mustache for Spring MVC found here in my project.
My understanding is that mustache.java raises a MustacheException by default when the template founds a variable that is resolved to be null. I would like for the Mustache compiler to resolve such values as an empty String instead.
I tried using the nullValue(String nullValue) function to set the appropriate behavior as seen in the code below, but it doesn't seem to have any effect. I understand that the obvious solution is to set the phoneNumber attribute to an empty value, but I would really like to understand why this particular code doesn't work.
You'll find below the code I use to test this behavior, which includes an Employee entity that purposefully doesn't instantiate its phoneNumber member value in its constructor and the relevant code snippets.
pom.xml
<dependency>
<groupId>com.github.sps.mustache</groupId>
<artifactId>mustache-spring-view</artifactId>
<version>1.3</version>
</dependency>
<!-- jmustache -->
<dependency>
<groupId>com.samskivert</groupId>
<artifactId>jmustache</artifactId>
<version>1.10</version>
</dependency>
<!-- mustache.java -->
<dependency>
<groupId>com.github.spullara.mustache.java</groupId>
<artifactId>compiler</artifactId>
<version>0.8.17</version>
</dependency>
Employee.java
public class Employee {
protected String firstName;
protected String lastName;
protected String phoneNumber;
public Employee() { }
public Employee(firstName, lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
// Getter and Setters for all attributes
}
getViewResolver
@Bean
public ViewResolver getViewResolver(ResourceLoader resourceLoader) {
MustacheViewResolver mustacheViewResolver = new MustacheViewResolver();
mustacheViewResolver.setPrefix("/src/main/resources/templates/");
mustacheViewResolver.setSuffix(".html");
mustacheViewResolver.setCache(false);
mustacheViewResolver.setContentType("text/html;charset=utf-8");
JMustacheTemplateLoader mustacheTemplateLoader = new JMustacheTemplateLoader();
mustacheTemplateLoader.setResourceLoader(resourceLoader);
JMustacheTemplateFactory mustacheTemplateFactory = new JMustacheTemplateFactory();
mustacheTemplateFactory.setTemplateLoader(mustacheTemplateLoader);
mustacheTemplateFactory.setCompiler(Mustache.compiler().nullValue(" "));
mustacheViewResolver.setTemplateFactory(mustacheTemplateFactory);
return mustacheViewResolver;
}
EmployeeController
@Autowired
private EmployeeRepository repository;
...
@RequestMapping(value = "/{id}", method = RequestMethod.GET)
public String viewEmployee(@PathVariable Long id, Model model) {
model.addAttribute("employee", repository.findOne(id));
return "employee_view";
}
employee_view.html
<!DOCTYPE html>
<html>
<body>
<ul>
{{#employee}}
<li> First Name: {{firstName}}
<li> Last Name: {{lastName}}
<li> Phone Number: {{phoneNumber}}
{{/employee}}
</ul>
</body>
</html>
557
asked Jun 04 '26 12:06
I am using spring-boot.1.2.5.RELEASE now.
If you check out org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration's source code (lines 73 ~ 78), you can tell defaultValue is not configurable.
May be you should make a new your own Spring Boot starter to fix it. Or you can use FreeMarker or Velocity instead it.
Or you can hack it with a BeanPostProcessor when ApplicationContext starts up.
Like this:
@Bean
public BeanPostProcessor mutacheHackerBeanPostProcessor() {
return new BeanPostProcessor() {
private static final String BEAN_NAME = "mustacheCompiler";
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (ClassUtils.isAssignable(bean.getClass(), Mustache.Compiler.class) || BEAN_NAME.equals(beanName)) {
System.out.println("----------");
System.out.println("hack ok!!!");
System.out.println("----------");
Mustache.Compiler compiler = (Mustache.Compiler) bean;
return compiler.defaultValue("").nullValue("");
}
return bean;
}
};
}
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