Spring BindingResult 教程展示了如何使用 BindingResult 来获取验证结果。
Spring 是用于创建企业应用的流行 Java 应用框架。
BindingResult
BindingResult保存验证和绑定的结果，并包含可能发生的错误。 BindingResult必须紧随经过验证的模型对象之后，否则 Spring 无法验证该对象并引发异常。
Spring BindingResult示例
以下应用验证用户表单，并使用 BindingResult 存储验证结果。
pom.xmlsrc├───main│ ├───java│ │ └───com│ │ └───zetcode│ │ ├───config│ │ │ MyWebInitializer.java│ │ │ WebConfig.java│ │ ├───controller│ │ │ MyController.java│ │ └───form│ │ UserForm.java│ └───resources│ └───templates│ form.html│ showInfo.html└───test └───java
这是项目结构。
pom.xml
<?xml version="1.0" encoding="UTF-8"?><project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.zetcode</groupId> <artifactId>bindingresultex</artifactId> <version>1.0-SNAPSHOT</version> <packaging>war</packaging> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>11</maven.compiler.source> <maven.compiler.target>11</maven.compiler.target> <spring-version>5.1.3.RELEASE</spring-version> <thymeleaf-version>3.0.11.RELEASE</thymeleaf-version> </properties> <dependencies> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-classic</artifactId> <version>1.2.3</version> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>4.0.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.hibernate.validator</groupId> <artifactId>hibernate-validator</artifactId> <version>6.0.10.Final</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>5.1.3.RELEASE</version> </dependency> <dependency> <groupId>org.thymeleaf</groupId> <artifactId>thymeleaf-spring5</artifactId> <version>{thymeleaf-version}</version> </dependency> <dependency> <groupId>org.thymeleaf</groupId> <artifactId>thymeleaf</artifactId> <version>{thymeleaf-version}</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-war-plugin</artifactId> <version>3.2.2</version> </plugin> <plugin> <groupId>org.eclipse.jetty</groupId> <artifactId>jetty-maven-plugin</artifactId> <version>9.4.14.v20181114</version> </plugin> </plugins> </build></project>在pom.xml文件中，我们具有项目依赖项。
<dependency> <groupId>org.hibernate.validator</groupId> <artifactId>hibernate-validator</artifactId> <version>6.0.10.Final</version></dependency>
我们使用hibernate-validator进行验证。
com/zetcode/config/MyWebInitializer.java
package com.zetcode.config;import org.springframework.context.annotation.Configuration;import org.springframework.web.context.WebApplicationContext;import org.springframework.web.servlet.DispatcherServlet;import org.springframework.web.servlet.FrameworkServlet;import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;@Configurationpublic class MyWebInitializer extends AbstractAnnotationConfigDispatcherServletInitializer { @Override protected Class<?>[] getRootConfigClasses() { return null; } @Override protected Class<?>[] getServletConfigClasses() { return new Class[]{WebConfig.class}; } @Override protected String[] getServletMappings() { return new String[]{"/"}; }}MyWebInitializer初始化 Spring Web 应用。 它包含一个配置类：WebConfig。
com/zetcode/config/WebConfig.java
package com.zetcode.config;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.ApplicationContext;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;import org.springframework.web.servlet.ViewResolver;import org.springframework.web.servlet.config.annotation.EnableWebMvc;import org.springframework.web.servlet.config.annotation.ViewResolverRegistry;import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;import org.thymeleaf.spring5.SpringTemplateEngine;import org.thymeleaf.spring5.templateresolver.SpringResourceTemplateResolver;import org.thymeleaf.spring5.view.ThymeleafViewResolver;@Configuration@EnableWebMvc@ComponentScan(basePackages = {"com.zetcode"})public class WebConfig implements WebMvcConfigurer { @Autowired private ApplicationContext applicationContext; @Bean public SpringResourceTemplateResolver templateResolver() { var templateResolver = new SpringResourceTemplateResolver(); templateResolver.setApplicationContext(applicationContext); templateResolver.setPrefix("classpath:/templates/"); templateResolver.setSuffix(".html"); return templateResolver; } @Bean public SpringTemplateEngine templateEngine() { var templateEngine = new SpringTemplateEngine(); templateEngine.setTemplateResolver(templateResolver()); templateEngine.setEnableSpringELCompiler(true); return templateEngine; } @Bean public ViewResolver viewResolver() { var resolver = new ThymeleafViewResolver(); var registry = new ViewResolverRegistry(null, applicationContext); resolver.setTemplateEngine(templateEngine()); registry.viewResolver(resolver); return resolver; }}WebConfig配置 Thymeleaf 模板引擎。 Thymeleaf 模板文件位于类路径的templates子目录中。
com/zetcode/form/UserForm.java
package com.zetcode.form;import javax.validation.constraints.Email;import javax.validation.constraints.NotBlank;import javax.validation.constraints.Size;public class UserForm { @NotBlank @Size(min=2) private String name; @NotBlank @Email private String email; public String getName() { return name; } public void setName(String name) { this.name = name; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; }}这是一个表单 bean。 它包含一些验证注释。
@NotBlank@Size(min=2)private String name;
name 属性不能为空，并且必须至少包含 2 个字符。
@NotBlank@Emailprivate String email;
email 属性不能为空，并且必须是格式正确的电子邮件。
com/zetcode/controller/MyController.java
package com.zetcode.controller;import com.zetcode.form.UserForm;import org.springframework.stereotype.Controller;import org.springframework.validation.BindingResult;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.ModelAttribute;import org.springframework.web.bind.annotation.PostMapping;import org.springframework.web.servlet.mvc.support.RedirectAttributes;import javax.validation.Valid;@Controllerpublic class MyController { @GetMapping(value = "/") public String form(UserForm userForm) { return "form"; } @PostMapping("/") public String checkForm(@Valid UserForm userForm, BindingResult bindingResult, RedirectAttributes atts) { if (bindingResult.hasErrors()) { return "form"; } atts.addAttribute("name", userForm.getName()); atts.addAttribute("email", userForm.getEmail()); return "redirect:/showInfo"; } @GetMapping("/showInfo") public String showInfo(@ModelAttribute("name") String name, @ModelAttribute("email") String email) { return "showInfo"; }}MyController包含请求路径到处理程序方法的映射。
@GetMapping(value = "/")public String form(UserForm userForm) { return "form";}主页返回一个包含表单的视图。 UserForm bean 正在支持表单。 它将使用来自表单的数据进行填充。
@PostMapping("/")public String checkForm(@Valid UserForm userForm, BindingResult bindingResult, RedirectAttributes atts) {...我们用@Valid验证UserForm bean。 验证结果存储在BindingResult中。
if (bindingResult.hasErrors()) { return "form";}如果绑定结果包含错误，我们将返回表格。
atts.addAttribute("name", userForm.getName());atts.addAttribute("email", userForm.getEmail());return "redirect:/showInfo";遵循发布后重定向模式，成功验证后，我们将重定向到showInfo视图。 为了不丢失输入，我们将它们存储在RedirectAttributes中。
@GetMapping("/showInfo")public String showInfo(@ModelAttribute("name") String name, @ModelAttribute("email") String email) { return "showInfo";}@ModelAttribute将请求属性 nad 放入模型对象，然后将其发送到showInfo视图。
resources/templates/form.html
<!DOCTYPE html><html xmlns:th="http://www.thymeleaf.org"><head> <meta charset="UTF-8"> <title>User form</title> <link href="https://cdnjs.cloudflare.com/ajax/libs/semantic-ui/2.3.1/semantic.min.css" rel="stylesheet"></head><body><section class="ui container"> <form action="#" class="ui form" th:action="@{/}" th:object="{userForm}" method="post"> <div class="field"> <label>Name:</label> <input type="text" th:field="*{name}"> <span th:if="{#fields.hasErrors('name')}" th:errors="*{name}">Name Error</span> </div> <div class="field"> <label>Email:</label> <input type="text" th:field="*{email}"> <span th:if="${#fields.hasErrors('email')}" th:errors="*{email}">Email Error</span> </div> <button class="ui button" type="submit">Submit</button> </form></section></body></html>
根页面包含表单。
<link href="https://cdnjs.cloudflare.com/ajax/libs/semantic-ui/2.3.1/semantic.min.css" rel="stylesheet">
表单使用语义 UI 设置样式。
<form action="#" class="ui form" th:action="@{/}" th:object="${userForm}" method="post">th:object引用用户表单 bean。 这不是一个类名，而是一个 Spring bean 名称。 因此它是小写的。
<input type="text" th:field="*{name}">输入被映射到userForm的name属性。
<span th:if="${#fields.hasErrors('name')}" th:errors="*{name}">Name Error</span>此行显示可能的验证错误。
resources/templates/showInfo.html
<!DOCTYPE html><html xmlns:th="http://www.thymeleaf.org"><head> <meta charset="UTF-8"> <title>Show info</title></head><body><p> Successfully added user <span th:text="{name}" th:remove="tag"></span> with email <span th:text="{email}" th:remove="tag"></span></p></body></html>此视图显示输入的信息。
在本教程中，我们在验证表单时使用了BindingResult。
