小编dav*_*xxx的帖子

我试图用很少的常量创建枚举.我希望枚举成为单身人士.使用下面的代码,我在eclipse中遇到编译错误:

语法错误,插入")"

在第5行完成方法声明.我无法找出错误.

public enum Days {

      SUNDAY,MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY;

      INSTANCE; // line 5

      public Days getInstance() {
        return INSTANCE;
     }
}

所以我只是在玩Spring Boot 2.0.4，我今天注意到了这一点。不知道我错过了什么。请帮我检查一下。

春季申请

@SpringBootApplication
@EnableScheduling
public class Application extends SpringBootServletInitializer {

application.properties（位于src / main / resources中）

server.port=8088

使用Intellij启动项目

2018-08-17 12:11:05 INFO  o.s.b.w.e.tomcat.TomcatWebServer - Tomcat started on port(s): 8088 (http) with context path ''

使用java命令行启动项目：

java -jar sample.jar --spring.config.location=D:\config\ --spring.profiles.active=dev

应用程序未使用配置的端口

2018-08-17 11:25:25 INFO  o.s.b.w.e.tomcat.TomcatWebServer - Tomcat started on port(s): 8080 (http) with context path ''

看起来Spring Boot 2.0忽略了默认属性文件（请注意：此配置仅在applications.properties中，其他位置无，因此不会与其他配置文件重叠）

我有

package com.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.support.SpringBootServletInitializer;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@SpringBootApplication
@ComponentScan(basePackages = {"hello","com.ensat.controllers"})
@EntityScan("com.ensat.entities")
public class Application extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Application.class);
    }

    public static void main(String[] args) throws Exception {
        SpringApplication.run(Application.class, args);
    }

}

ProductController.java

package com.ensat.controllers;

import com.ensat.entities.Product;
import com.ensat.services.ProductService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

/**
 * Product controller.
 */
@Controller
public class …

关于如何访问mysql数据,我在启动spring指南时遇到了一些问题(请参阅此链接:https://spring.io/guides/gs/accessing-data-mysql/).我稍微调整了类,所以我有这个代码:

1. 的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>org.springframework</groupId>
       <artifactId>gs-mysql-data</artifactId>
       <version>0.1.0</version>
   
       <parent>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-parent</artifactId>
   <version>1.5.6.RELEASE</version>
   </parent>
   
   <dependencies>
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-web</artifactId>
   </dependency>
   
   <!-- JPA Data (We are going to use Repositories, Entities, Hibernate, etc...) -->
   
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-data-jpa</artifactId>
   </dependency>
   
   <!-- Use MySQL Connector-J -->
   
   <dependency>
       <groupId>mysql</groupId>
       <artifactId>mysql-connector-java</artifactId>
   </dependency>
   
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-test</artifactId>
       <scope>test</scope>
   </dependency>
   
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-jdbc</artifactId>
   </dependency>
   </dependencies>
   
   <properties>
       <java.version>1.8</java.version>
   </properties>
   
   <build>
   <plugins>
       <plugin>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-maven-plugin</artifactId>
       </plugin>
   </plugins>
   </build>
   

   Run Code Online (Sandbox Code Playgroud)

我正在使用这个mainController: MainController.java

import org.springframework.beans.factory.annotation.Autowired;
import …

我有一个实用方法,其目标是将a转换Collection为a Map.但是,当我尝试使用泛型时,它会出现编译错误,并且想知道如何修复它:

public static <K, V> Map<K, V> convertCollectionToMap(Collection<V extends ListToMapConvertable<K, V>> sourceList) {
    Map<K, V> newMap = new HashMap<K, V>();
    for (V item : sourceList) {
        newMap.put(item.getKey(item), item);
    }

    return newMap;
} 

public interface ListToMapConvertable<K, V> {
    public K getKey(V item);
}

相反,我收到Incorrect number of arguments for type Collection<E>; it cannot be parameterized with arguments <V, ListToMapConvertable>编译错误.我不明白这个问题V只是延伸 ListToMapConverable.那么为什么它声称我使用了两个参数 - <V, ListToMapConvertable>？我该如何解决这个问题呢？

有spring boot 2.0.2配置

@Configuration
public class ApiConfig {

    @Bean
    @Profile("!tests")
    @ConditionalOnProperty(name = "enabled", havingValue = "true")
    public MyService service() {
        return new MyServiceImpl();
    }

}

...以及一些控制器，只有在初始化 MyService bean 时才应该创建并添加到应用程序上下文中。

@RestController
@ConditionalOnBean(MyService.class)
public class MyController {
   @Autowired
   private MyService service;
}

它工作正常。但偶尔春季启动会跳过 MyController 创建。根据日志 MyService 被创建，但在任何其他 bean（包括所有控制器）之后，最后。

为什么 boot@Configuration之前不处理bean @RestController？谢谢。

我继承了一个孤立的Java 8 / Maven项目，并试图确定其构建方式。在自述文件中，我看到了运行以下命令的说明：

mvn -o -q -Dexec.executable="echo" -Dexec.args='${project.version}' org.codehaus.mojo:exec-maven-plugin:exec

当我从我的项目根目录（包含pom.xml）运行该表单时，出现以下错误：

[ERROR] Error resolving version for plugin 'org.codehaus.mojo:exec-maven-plugin' from the repositories [local (/Users/myuser/.m2/repository), central (https://repo.maven.apache.org/maven2)]: Plugin not found in any plugin repository -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the …

有没有办法只使用lambdas执行以下代码？

// translate someList1 to someList3
// .. get sublist
List<String> someList2 = someList1.stream()
        .map(i -> i.getField())
        .collect(Collectors.toList());
// .. create new (target) list
List<SomeClass> someList3 = new ArrayList<>();
for (String item : someList2) {
    SomeClass someObj = new SomeClass();
    someObj.setField(item);
    someList3.add(someObj);
}

我使用 jpa、hibernate、spring boot - data、api REST 技术。

我有以下错误：

org.springframework.beans.factory.UnsatisfiedDependencyException：创建名为“walletRestService”的bean时出错：通过字段“walletRepository”表达的不满意依赖；嵌套异常是 org.springframework.beans.factory.BeanCreationException：创建名为“walletRepository”的 bean 时出错：调用 init 方法失败；嵌套异常是 java.lang.IllegalArgumentException: Failed to create query method public abstract java.lang.Long com.wj.dao.WalletRepository.createWallet(java.lang.Long,java.lang.String)！找不到类型 Wallet 的属性 createWallet！

这是我的代码：

实体用户：

package com.wj.entities;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;

import com.fasterxml.jackson.annotation.JsonManagedReference;

@Entity
public class User implements Serializable{

@Id
@GeneratedValue
private Long id; 
private String name;

@OneToMany(mappedBy="user", fetch=FetchType.LAZY)
@JsonManagedReference
private List<Wallet> wallets = new ArrayList<>();

public User() {
    super();
}

public User(String name) …

我有2个方法,它执行80%相同的工作,但结果处理不同.我在做 :

 private <T> T getResponse(final RestURI query, final Class<T> responseClass) throws IOException {
        T response = null;

        final RestResponse<Record> tempResponse = getResponseFromDataPath(query);

        if (isResponseOK(tempResponse, query)) {
            final CustomReader reader = createCustomReaderFromResponse(tempResponse);
            response = objectMapper.readValue(reader, responseClass);
                                                          ^
            // DIFFERENCE --------------------------------|
        }

        return response;
    }

    private <T> T getResponse(final RestURI query, final TypeReference valueTypeRef) throws IOException {
        T response = null;

        final RestResponse<Record> tempResponse = getResponseFromDataPath(query);

        if (isResponseOK(tempResponse, query)) {
            final CustomReader reader = createCustomReaderFromResponse(tempResponse);
            response = objectMapper.readValue(reader, valueTypeRef);
                                                          ^
            // …