# Spring `BindingResult`教程

> 原文： [http://zetcode.com/spring/bindingresult/](http://zetcode.com/spring/bindingresult/)

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。

```java
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`

```java
<?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。

```java
<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`

```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。 它包含一个配置类：`WebConfig`。

`com/zetcode/config/WebConfig.java`

```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`

```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。

```java
@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。

```java
@NotBlank
@Email
private 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`

```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器方法的映射。

```java
@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。

```java
@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。

```java
if (bindingResult.hasErrors()) {
    return "form";
}

```

如果绑定结果包含错误，我们将返回表格。

```java
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。

```java
@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`

```java
<!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。

```java
<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。

```java
<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。

```java
<input type="text" th:field="*{name}">

```

输入被映射到`userForm`的`name`属性。

```java
<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`

```java
<!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`。

您可能也对这些相关教程感兴趣： [Spring `@GetMapping`教程](/spring/getmapping/)， [Spring `DefaultServlet`教程](/spring/defaultservlet/)， [Spring Web 应用简介](/articles/springwebfirst/)和 [Java 教程](/lang/java/)。