Java tutorial
package urlshortener2014.oldBurgundy.web.errorcontroler; /* * Copyright 2012-2014 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import java.io.StringWriter; import java.util.HashMap; import java.util.List; import java.util.Map; import javax.servlet.Servlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.velocity.VelocityContext; import org.apache.velocity.app.Velocity; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Value; import org.springframework.boot.autoconfigure.AutoConfigureBefore; import org.springframework.boot.autoconfigure.EnableAutoConfiguration; import org.springframework.boot.autoconfigure.condition.ConditionOutcome; import org.springframework.boot.autoconfigure.condition.ConditionalOnClass; import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean; import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty; import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication; import org.springframework.boot.autoconfigure.condition.SearchStrategy; import org.springframework.boot.autoconfigure.condition.SpringBootCondition; import org.springframework.boot.autoconfigure.template.TemplateAvailabilityProvider; import org.springframework.boot.autoconfigure.web.BasicErrorController; import org.springframework.boot.autoconfigure.web.DefaultErrorAttributes; import org.springframework.boot.autoconfigure.web.ErrorAttributes; import org.springframework.boot.autoconfigure.web.ErrorController; import org.springframework.boot.autoconfigure.web.ServerProperties; import org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration; import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer; import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer; import org.springframework.boot.context.embedded.ErrorPage; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.ConditionContext; import org.springframework.context.annotation.Conditional; import org.springframework.context.annotation.Configuration; import org.springframework.context.expression.MapAccessor; import org.springframework.core.Ordered; import org.springframework.core.io.support.SpringFactoriesLoader; import org.springframework.core.type.AnnotatedTypeMetadata; import org.springframework.expression.Expression; import org.springframework.expression.spel.standard.SpelExpressionParser; import org.springframework.expression.spel.support.StandardEvaluationContext; import org.springframework.http.HttpHeaders; import org.springframework.http.HttpStatus; import org.springframework.http.MediaType; import org.springframework.http.ResponseEntity; import org.springframework.util.PropertyPlaceholderHelper; import org.springframework.util.PropertyPlaceholderHelper.PlaceholderResolver; import org.springframework.web.servlet.DispatcherServlet; import org.springframework.web.servlet.View; import org.springframework.web.servlet.view.BeanNameViewResolver; import org.springframework.web.util.HtmlUtils; /** * {@link EnableAutoConfiguration Auto-configuration} to render errors via a MVC error * controller. * * @author Dave Syer * @author Andy Wilkinson */ @ConditionalOnClass({ Servlet.class, DispatcherServlet.class }) @ConditionalOnWebApplication // Ensure this loads before the main WebMvcAutoConfiguration so that the error View is // available @AutoConfigureBefore(WebMvcAutoConfiguration.class) @Configuration public class ErrorMvcAutoConfiguration implements EmbeddedServletContainerCustomizer, Ordered { @Value("${error.path:/error}") private String errorPath = "/error"; @Autowired private ServerProperties properties; @Override public int getOrder() { return 0; } @Bean @ConditionalOnMissingBean(value = ErrorAttributes.class, search = SearchStrategy.CURRENT) public DefaultErrorAttributes errorAttributes() { return new DefaultErrorAttributes(); } @Bean @ConditionalOnMissingBean(value = ErrorController.class, search = SearchStrategy.CURRENT) public BasicErrorController basicErrorController(ErrorAttributes errorAttributes) { return new BasicErrorController(errorAttributes); } @Override public void customize(ConfigurableEmbeddedServletContainer container) { container.addErrorPages(new ErrorPage(this.properties.getServletPrefix() + this.errorPath)); } public static ResponseEntity<?> responseError(HttpStatus httpStatus) { StringWriter writer = new StringWriter(); VelocityContext context = new VelocityContext(); context.put("error", httpStatus.getReasonPhrase()); context.put("status", httpStatus); context.put("img", "http://localhost:8080/img/" + httpStatus + ".jpg"); Velocity.mergeTemplate("err.vm", "ISO-8859-1", context, writer); HttpHeaders h = new HttpHeaders(); h.setContentType(MediaType.TEXT_HTML); return new ResponseEntity<>(writer.toString(), h, HttpStatus.NOT_FOUND); } @Configuration @ConditionalOnProperty(prefix = "error.whitelabel", name = "enabled", matchIfMissing = true) @Conditional(ErrorTemplateMissingCondition.class) protected static class WhitelabelErrorViewConfiguration { @Bean(name = "error") @ConditionalOnMissingBean(name = "error") public static View defaultErrorView() { StringWriter writer = new StringWriter(); VelocityContext context = new VelocityContext(); context.put("error", "${error}"); context.put("status", "${status}"); context.put("img", "http://localhost:8080/img/" + "${status}" + ".jpg"); Velocity.mergeTemplate("err.vm", "ISO-8859-1", context, writer); SpelView defaultErrorView = new SpelView(writer.toString()); return (defaultErrorView); } // If the user adds @EnableWebMvc then the bean name view resolver from // WebMvcAutoConfiguration disappears, so add it back in to avoid disappointment. @Bean @ConditionalOnMissingBean(BeanNameViewResolver.class) public BeanNameViewResolver beanNameViewResolver() { BeanNameViewResolver resolver = new BeanNameViewResolver(); resolver.setOrder(Ordered.LOWEST_PRECEDENCE - 10); return resolver; } } /** * {@link SpringBootCondition} that matches when no error template view is detected. */ private static class ErrorTemplateMissingCondition extends SpringBootCondition { @Override public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) { List<TemplateAvailabilityProvider> availabilityProviders = SpringFactoriesLoader .loadFactories(TemplateAvailabilityProvider.class, context.getClassLoader()); for (TemplateAvailabilityProvider availabilityProvider : availabilityProviders) { if (availabilityProvider.isTemplateAvailable("error", context.getEnvironment(), context.getClassLoader(), context.getResourceLoader())) { return ConditionOutcome .noMatch("Template from " + availabilityProvider + " found for error view"); } } return ConditionOutcome.match("No error template view detected"); } } /** * Simple {@link View} implementation that resolves variables as SpEL expressions. */ private static class SpelView implements View { private final String template; private final StandardEvaluationContext context = new StandardEvaluationContext(); private PropertyPlaceholderHelper helper; private PlaceholderResolver resolver; public SpelView(String template) { this.template = template; this.context.addPropertyAccessor(new MapAccessor()); this.helper = new PropertyPlaceholderHelper("${", "}"); this.resolver = new SpelPlaceholderResolver(this.context); } @Override public String getContentType() { return "text/html"; } @Override public void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception { if (response.getContentType() == null) { response.setContentType(getContentType()); } Map<String, Object> map = new HashMap<String, Object>(model); map.put("path", request.getContextPath()); this.context.setRootObject(map); String result = this.helper.replacePlaceholders(this.template, this.resolver); response.getWriter().append(result); } } /** * SpEL based {@link PlaceholderResolver}. */ private static class SpelPlaceholderResolver implements PlaceholderResolver { private final SpelExpressionParser parser = new SpelExpressionParser(); private final StandardEvaluationContext context; public SpelPlaceholderResolver(StandardEvaluationContext context) { this.context = context; } @Override public String resolvePlaceholder(String name) { Expression expression = this.parser.parseExpression(name); try { Object value = expression.getValue(this.context); return HtmlUtils.htmlEscape(value == null ? null : value.toString()); } catch (Exception ex) { return null; } } } }