Spring Boot，JPA和MySQL返回空結果

Question

好吧我是Java Spring的新手，我只是試圖從MYSQL數據庫訪問一些數據。不幸的是，我似乎無法加載任何數據 - 我敢肯定這是一個愚蠢的錯誤。 （我已經按照多種來源，包括this one）

我使用： java的春天開機，MySQL和JPA，gradle這個

這裏是我的build.gradle：

buildscript { 
    repositories { 
     mavenCentral() 
    } 
    dependencies { 
     classpath("org.springframework.boot:spring-boot-gradle-plugin:1.3.2.RELEASE") 
    } 
} 

apply plugin: 'java' 
apply plugin: 'eclipse' 
apply plugin: 'idea' 
apply plugin: 'spring-boot' 

jar { 
    baseName = 'gs-serving-web-content' 
    version = '0.1.0' 
} 

repositories { 
    mavenCentral() 
} 

sourceCompatibility = 1.8 
targetCompatibility = 1.8 

dependencies { 
    compile("org.springframework.boot:spring-boot-starter-web") 
    compile("org.springframework.boot:spring-boot-starter-thymeleaf") 
    compile("org.springframework.boot:spring-boot-starter-data-jpa") 

    compile("com.h2database:h2") //I get embedded db error if I take this out 
    testCompile("junit:junit") 
    compile('mysql:mysql-connector-java:5.1.35') 
} 

task wrapper(type: Wrapper) { 
    gradleVersion = '2.3' 
} 

控制器：

@Controller 
public class PersonController { 
    @Autowired 
    private PersonRepository personRepository; 

    @RequestMapping(value = "/hello", method = RequestMethod.GET) 
public String greeting(...){ 
    List<Person> allPeople = personRepository.findAll(); //this comes back with 0 values 
    ... 
} 

PersonRepository：

public interface PersonRepository extends JpaRepository<Person, Long> { 
List<Person> findAll(); //returns empty list 

//Person findByAge(int Age); //throws an exception if I leave this on: "...nested exception is java.lang.IllegalArgumentException: Could not create query metamodel for method public abstract hello.model.Person hello.repository.PersonRepository.findByAge(int)!" 
} 

人：

@Entity 
@Table(name="person") 
public class Person { 
    @Id 
    @GeneratedValue(strategy = GenerationType.AUTO) 
    private long PersonID; 
    private String Firstname; 
    private String Lastname; 
    private int Age; 
    //getters and setters 
} 

Application.yaml

spring: 
datasource: 
    url: jdbc:mysql://localhost:3306/datatest 
    username: root 
    password: *** 
    driverClassName: com.mysql.jdbc.Driver 

我的IntelliJ連接成功MySQL數據庫（數據庫標籤下） ，我可以從標籤罰款查詢它，但我無法通過彈簧加載數據。考慮到我無法刪除嵌入的h2數據庫，除非有例外，我的設置中肯定有問題，我也不能添加findByAge,findByFirstname等組合（全都拋出異常）。

更新1：我申請HD1的Person類的變化，但我仍然沒有得到任何數據傳回：

@Entity 
@Table(name="person") 
public class Person { 
    @Id 
    @GeneratedValue(strategy = GenerationType.AUTO) 
    private long personID; 
    private String firstName; 
    private String lastName; 
    private int age; 
    //getters and setters updated 

PersonRepository：

List<Person> findAll(); 
Person findByAge(int age); //no more errors here, but returns null 
Person findByLastName(String lastName); //no more errors here, but returns null 

Full Runlog file

更新2：控制器方法：

@RequestMapping(value = "/hello", method = RequestMethod.GET) 
public String greeting(@RequestParam(value = "name", required = false, defaultValue = "world") String name, Model model) { 
    List<Person> allPeople = personRepository.findAll(); 
     ... 
    System.out.print(allPeople.size()); //always 0, but I have many entries in db 

    //if I try to create and save new entry in the db: 
    Person person = new Person(); 
    person.setFirstName("New"); 
    person.setLastName("Person"); 
    person.setAge(99); 
    personRepository.save(person); //does not show up in DB, why? 
    return "greeting"; 
} 

Answer 1

顯然，你不跟着你的鏈接教程，因爲屬性名稱是駝峯那裏和這裏的首字母大寫。 Spring需要camelCase的屬性，因爲entity scanner uses camelCase for accessor/mutator generation。

[根據註釋]

在PersonRepository，嘗試取消註釋註釋行。如果仍有問題，請在下次編輯中發佈完整的堆棧跟蹤和runlog。

Answer 2

你應該使用小寫的屬性

private long personID; 
private String firstname; 
private String lastname; 
private int age; 

我測試過，並得到同樣的異常。但有其最高審計機關嵌套異常：

Unable to locate Attribute with the the given name [attributename]