【发布时间】：2017-08-06 12:40:13
【问题描述】：
我正在编写一个可以访问数据库以查看、添加和更新 mysql 表中的字段的休息服务。我已经用 Spring Boot 实现了这一点。
事实是，当我尝试自动装配 DAO 对象时它不起作用，它为 null，所以我的应用程序总是抛出 NullPointerException。
这是我的应用程序类：
@SpringBootApplication
@EnableSwagger2
@ComponentScan(basePackages = "com.setoncios.api")
@EnableJpaRepositories("com.setoncios.api.dao.workers.WorkerDAO.java")
public class GenericApiApplication {
public static void main(String[] args) {
SpringApplication.run(GenericApiApplication.class, args);
}
@Bean
public Docket swaggerSettings() {
return new Docket(DocumentationType.SWAGGER_2)
.select()
.apis(RequestHandlerSelectors.any())
.paths(PathSelectors.any())
.build()
.pathMapping("/");
}
这是我的 pom.xml：
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
</dependency>
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger-ui</artifactId>
<version>2.6.1</version>
</dependency>
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger2</artifactId>
<version>2.6.1</version>
</dependency>
</dependencies>
这是我的 DAO 实现：
@Component
public interface WorkerDAO extends CrudRepository<Persona,String>{
}
包含抛出异常的方法的rest方法：
@RequestMapping(value = "/worker", method = RequestMethod.POST)
public ResponseEntity<?> addWorkerInDatabase(HttpServletRequest request,
@RequestParam(value = "json", defaultValue =
"{\"dni\":\"00000000A\",\"nombre\":\"Paco\",\"apellido1\":\"Ruiz\",\"apellido2\":\"Díaz\"}") final String json){
ProcessAction object = new AddWorkerInDatabaseAction(request, json);
return object.createResponse();
}
还有课程本身：
public class AddWorkerInDatabaseAction extends ProcessAction{
private String json;
@Autowired
private UserDatabase userDb = new UserDatabase();
@Autowired
private WorkerDAO workDb;
public AddWorkerInDatabaseAction(HttpServletRequest request, String json) {
super(request);
this.json = json;
}
@Override
protected Object action() throws ExpectedException {
Persona newWorker = new Gson().fromJson(json, Persona.class);
Cookie c = findCookie("userdata");
String[] loggedUser = null;
if(newWorker == null){
LOGGER.warning("Unable to decrypt from json to Persona.");
} else if(c == null){
LOGGER.info("Couldn't find cookie. Unable to add a worker.");
newWorker = null;
} else {
try {
userDb.connect();
loggedUser = c.getValue().split(":");
if(!loggedUser[0].equals("00000000A") || !loggedUser[1].equals(userDb.selectPassword("00000000A"))){
LOGGER.warning("You need privileges to add a worker.");
} else if(newWorker.getNombre() == null || newWorker.getApellido1() == null || newWorker.getApellido2() == null){
workDb.save(newWorker); //Here's where the exception is being thrown.
} else {
workDb.save(newWorker); //Here's where the exception is being thrown.
}
} catch (ClassNotFoundException e) {
userDb.rollback();
newWorker = null;
LOGGER.warning("Exception with driver encountered.");
throw new ExpectedException(1, e.getMessage());
} catch (SQLException e) {
userDb.rollback();
newWorker = null;
throw new ExpectedException(2, e.getMessage());
} finally {
userDb.commit();
userDb.disconnect();
}
}
return newWorker;
}
}
我已经阅读了很多帖子，但我找不到可行的方法。有没有我错过的注释？
提前谢谢你：3
编辑。应用答案后，我的主要课程：
@SpringBootApplication
@EnableSwagger2
@ComponentScan(basePackages = "com.setoncios.api")
@EnableJpaRepositories("com.setoncios.api.dao.workers")
public class GenericApiApplication {
public static void main(String[] args) {
SpringApplication.run(GenericApiApplication.class, args);
}
@Bean
public Docket swaggerSettings() {
return new Docket(DocumentationType.SWAGGER_2)
.select()
.apis(RequestHandlerSelectors.any())
.paths(PathSelectors.any())
.build()
.pathMapping("/");
}
}
其余方法：
@RequestMapping(value = "/worker", method = RequestMethod.POST)
public ResponseEntity<?> addWorkerInDatabase(HttpServletRequest request,
@RequestParam(value = "json", defaultValue =
"{\"dni\":\"00000000A\",\"nombre\":\"Paco\",\"apellido1\":\"Ruiz\",\"apellido2\":\"Díaz\"}") final String json){
return addDB.createResponse(request, json);
}
还有 AddWorkerInDatabaseAction 类：
@Service
public class AddWorkerInDatabaseAction extends ProcessAction{
@Autowired
private UserDatabase userDb = new UserDatabase();
@Autowired
private WorkerDAO workDb;
public AddWorkerInDatabaseAction() {
}
@Override
protected Object action(Object...args) throws ExpectedException {
Persona newWorker = new Gson().fromJson((String) args[1], Persona.class);
workDb.save(newWorker);
return newWorker;
}
}
希望对某人有所帮助。
【问题讨论】：
-
你不应该用
new操作符创建AddWorkerInDatabaseAction类的对象，你应该自动装配它。 -
我之所以这样做，是因为有更多来自 ProcessAction 的操作。通过这种方式，我试图区分它们。我会尝试寻找其他方法来改善这一点。
标签： java mysql spring spring-boot dao