Java thymeleaf错误：org.springframework.expression.spel.SpelEvaluationException_Java_Spring Boot_Thymeleaf

Java thymeleaf错误：org.springframework.expression.spel.SpelEvaluationException

java spring-boot

Java thymeleaf错误：org.springframework.expression.spel.SpelEvaluationException,java,spring-boot,thymeleaf,Java,Spring Boot,Thymeleaf,预期的内容数据绑定后，网页应该反映数据详细信息控制器代码 RequestData.java public class RequestData { private String id; private String content; public String getId() { return id; } public void setId(String id) { this.id = id; }

预期的内容

数据绑定后，网页应该反映数据

详细信息

控制器代码

RequestData.java

public class RequestData {

    private String id;
    private String content;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

}

Credentials.java

@Component
@Configuration
@PropertySource("classpath:application.properties")
public class Credentials {

    public String userName;
    public String password;

     @Autowired
     private Environment env;

    @Autowired
    public String getUserName() {

         return env.getProperty("spring.username");

            }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    @Autowired
    public String getPassword() {
         return env.getProperty("spring.password");

            }

    public void setPassword(String password) {
        this.password = password;
    }


}

result.html

 <!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
<head> 
    <title>Hello World</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
    <h1>Hello World</h1>
    <p th:text="'id: ' + ${greeting.id}" />
    <p th:text="'content: ' + ${greeting.content}" />
    <a href="/greeting">Submit another message</a>
</body>
</html>

我不确定问题在哪里，thymeleaf doc说，模型属性可以通过${attributeName}访问，我也使用的是相同的，但是为什么它说“找不到id”

请从Spring mvc文档中提出建议，我引用-

如果没有显式指定模型属性名称，会发生什么情况？在这种情况下，将根据模型属性指定默认名称关于它的类型。例如，如果该方法返回类型为的对象 Account，使用的默认名称为“Account”。你可以改变通过@modeldattribute注释的值。如果添加属性直接添加到模型中，请使用适当的重载 addAttribute（..）方法-即，有或没有属性名称

就你而言

@PostMapping("/greeting")
public String greetingSubmit(@ModelAttribute("greeting) RequestData greeting) {
..
}

是否确实调用了greetingForm方法？

2018-10-31 15:36:34.259 ERROR 8220 --- [nio-8080-exec-4] o.a.c.c.C.[.[.[/].[disp
atcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context
 with path [] threw exception [Request processing failed; nested exception is or
g.thymeleaf.exceptions.TemplateProcessingException: Exception evaluating SpringE
L expression: "greeting.id" (template: "result" - line 9, col 8)] with root caus
e

org.springframework.expression.spel.SpelEvaluationException: EL1007E: Property o
r field 'id' cannot be found on null

@PostMapping("/greeting")
public String greetingSubmit(@ModelAttribute("greeting) RequestData greeting) {
..
}