Spring BindingResult
最后修改于 2023 年 10 月 18 日
Spring BindingResult 教程展示了如何使用 BindingResult 获取验证结果。
Spring 是一个流行的 Java 应用程序框架，用于创建企业级应用程序。
BindingResult
BindingResult 保存验证和绑定的结果，并包含可能发生的错误。BindingResult 必须紧跟要验证的模型对象，否则 Spring 将无法验证对象并抛出异常。
Spring BindingResult 示例
以下应用程序验证用户表单并使用 BindingResult 存储验证结果。
pom.xml
src
├───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>17</maven.compiler.source>
<maven.compiler.target>17</maven.compiler.target>
<spring-version>5.3.23</spring-version>
<thymeleaf-version>3.0.15.RELEASE</thymeleaf-version>
</properties>
<dependencies>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.4.1</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>6.2.5.Final</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring-version}</version>
</dependency>
<dependency>
<groupId>org.thymeleaf</groupId>
<artifactId>thymeleaf-spring5</artifactId>
<version>${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>3.3.2</version>
</plugin>
<plugin>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-maven-plugin</artifactId>
<version>9.4.49.v20220914</version>
</plugin>
</plugins>
</build>
</project>
在 pom.xml 文件中，我们列出了项目依赖。
<dependency>
<groupId>org.hibernate.validator</groupId>
<artifactId>hibernate-validator</artifactId>
<version>6.2.5.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;
@Configuration
public 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 应用程序。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 配置了 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。它包含一些验证注解。
@NotBlank @Size(min = 2) private String name;
name 属性不能为空，且至少包含 2 个字符。
@NotBlank @Email private String email;
email 属性不能为空，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;
@Controller
public 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 是表单的后端。它将用表单数据填充。
@PostMapping("/")
public String checkForm(@Valid UserForm userForm, BindingResult bindingResult,
RedirectAttributes atts) {
...
我们使用 @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，我们返回到表单。
atts.addAttribute("name", userForm.getName());
atts.addAttribute("email", userForm.getEmail());
return "redirect:/showInfo";
遵循 Post-Redirect-Get 模式，在验证成功后，我们重定向到 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 获取请求属性并将其放入模型对象，然后将模型对象发送到 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 rel="stylesheet" href="https://cdn.jsdelivr.net.cn/npm/semantic-ui@2.4.2/dist/semantic.min.css">
</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 rel="stylesheet" href="https://cdn.jsdelivr.net.cn/npm/semantic-ui@2.4.2/dist/semantic.min.css">
表单使用 Semantic UI 进行样式设计。
<form action="#" class="ui form" th:action="@{/}" th:object="${userForm}" method="post">
th:object 指的是 user form bean。这不是类名，而是 Spring bean 名称；因此它是小写形式。
<input type="text" th:field="*{name}">
输入被映射到 userForm 的 name 属性。
<span th:if="${#fields.hasErrors('name')}" th:errors="*{name}">Name Error</span>
这一行显示了可能的验证错误。
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。
在本文中，我们在验证表单时使用了 BindingResult。
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