Created
February 8, 2019 01:54
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Null rendering in thymeleaf
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| package com.example.demo; | |
| import java.util.Collection; | |
| import org.springframework.beans.factory.ObjectProvider; | |
| import org.springframework.boot.SpringApplication; | |
| import org.springframework.boot.autoconfigure.SpringBootApplication; | |
| import org.springframework.context.annotation.Bean; | |
| import org.thymeleaf.context.IExpressionContext; | |
| import org.thymeleaf.dialect.IDialect; | |
| import org.thymeleaf.spring5.SpringTemplateEngine; | |
| import org.thymeleaf.spring5.dialect.SpringStandardDialect; | |
| import org.thymeleaf.spring5.expression.SPELVariableExpressionEvaluator; | |
| import org.thymeleaf.standard.expression.IStandardVariableExpression; | |
| import org.thymeleaf.standard.expression.IStandardVariableExpressionEvaluator; | |
| import org.thymeleaf.standard.expression.StandardExpressionExecutionContext; | |
| import org.thymeleaf.templateresolver.ITemplateResolver; | |
| @SpringBootApplication | |
| public class DemoApplication { | |
| @Bean | |
| public SpringTemplateEngine templateEngine( | |
| Collection<ITemplateResolver> templateResolvers, | |
| ObjectProvider<IDialect> dialects) { | |
| SpringTemplateEngine engine = new SpringTemplateEngine(); | |
| templateResolvers.forEach(engine::addTemplateResolver); | |
| dialects.orderedStream().forEach(engine::addDialect); | |
| engine.setDialect(new ExtendedSpringDialect()); | |
| return engine; | |
| } | |
| public static void main(String[] args) { | |
| SpringApplication.run(DemoApplication.class, args); | |
| } | |
| private static class ExtendedSpringDialect extends SpringStandardDialect { | |
| @Override | |
| public IStandardVariableExpressionEvaluator getVariableExpressionEvaluator() { | |
| return NullSafeSPELVariableExpressionEvaluator.INSTANCE; | |
| } | |
| } | |
| private static class NullSafeSPELVariableExpressionEvaluator implements | |
| IStandardVariableExpressionEvaluator { | |
| private static final NullSafeSPELVariableExpressionEvaluator INSTANCE = new NullSafeSPELVariableExpressionEvaluator(); | |
| @Override | |
| public Object evaluate(IExpressionContext context, | |
| IStandardVariableExpression expression, | |
| StandardExpressionExecutionContext expContext) { | |
| return postProcess(SPELVariableExpressionEvaluator.INSTANCE.evaluate(context, | |
| expression, expContext)); | |
| } | |
| private Object postProcess(Object result) { | |
| if (result == null) { | |
| return "- -"; | |
| } | |
| return result; | |
| } | |
| } | |
| } |
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| <!DOCTYPE HTML> | |
| <html xmlns:th="http://www.thymeleaf.org"> | |
| <head> | |
| <title>Getting Started: Serving Web Content</title> | |
| <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> | |
| </head> | |
| <body> | |
| <p th:text="'Hello, ' + ${{first}} + ' ' + ${{last}} + '!'" /> | |
| </body> | |
| </html> |
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| package com.example.demo; | |
| import org.springframework.stereotype.Controller; | |
| import org.springframework.web.bind.annotation.RequestMapping; | |
| import org.springframework.web.servlet.ModelAndView; | |
| @Controller | |
| public class MyController { | |
| @RequestMapping("/hello") | |
| public ModelAndView hello() { | |
| ModelAndView modelAndView = new ModelAndView("hello"); | |
| modelAndView.addObject("first", "Phil"); | |
| modelAndView.addObject("last", null); | |
| return modelAndView; | |
| } | |
| } |
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