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Spring Boot FAQ

• 大数据 • 阅读 75

eclipse 在marketPlace安装lombok, springtool4, dbeaver,docker tooling

  1. tomcat的端口,数据连接这些都存在resourcces/application.yml里

Loading class com.mysql.jdbc.Driver'. This is deprecated. The new driver class iscom.mysql.cj.jdbc.Driver’. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.

server:
  port: 8082

spring:
 datasource:
  driverClassName: com.mysql.cj.jdbc.Driver
  url: jdbc:mysql://localhost:3307/test?useSSL=false&useUnicode=true&characterEncoding=utf8
  username: root
  password: root

  1. 自动导入 点击File—>Settings .Editor—>General—>Auto Import IDEA默认自动导入的快捷键是：Alt+Enter

  2. 未配置 SQL 方言。 idea->File->Settings->Languages & Frameworks->SQL Dialects

Spring Boot FAQ

  1. 不建议使用字段注入. 但这个写法很省事, Spring中为什么不建议使用字段注入 – EchoLv – 博客园 (cnblogs.com)

  2. @SpringBootApplication 是一个配置类,它会自动扫描所有Spring Bean( 由Spring框架IOC创建的对象),

SpringBootApplication is a configuration class. It then begins autoscanning all the classes on the Java classpath for other Spring beans.

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args); //返回一个Spring ApplicationContext 对象。

}

}

A Spring bean is an object that the Spring framework manages at run time with the Inversion of Control (IoC) container.

These are created and added to a “repository of objects” so you can get them later.

只有在容器中的组件，才会拥有 SpringBoot 提供的强大功能。首先就要保证该对 JavaBean 对象在 IoC 容器中，所以需要用到 @Component 注解来添加组件到容器中。

_ Spring容器来说，当我们把一个Bean标记为 @Component后，它就会自动为我们创建一个单例（Singleton)_

_ 还有一种Bean，我们每次调用 getBean(Class)，容器都返回一个新的实例，这种Bean称为Prototype（原型），它的生命周期显然和Singleton不同。声明一个Prototype的Bean时，需要添加一个额外的 @Scope注解：_

<span class="annotation">@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE) </span>

@ConfigurationProperties(prefix = “person”) 从yml文件读取时间,会默认yml文件的时间是加了时区的, 当你打印出来默认会改成GMT时间

yml文件

person:
  lastName: 张三
  age: 18
  boss: false
  birth: 1990/12/12
  maps: { k1: v1,k2: 12 }
  lists:
    ‐ lisi
    ‐ zhaoliu
  dog:
    name: 迪迪
    age: 5

在网页JSON输出

{"lastName":"张三","age":18,"boss":false,"birth":"1990-12-11T16:00:00.000+0000","maps":{"k1":"v1","k2":12},"lists":["‐ lisi ‐ zhaoliu"],"dog":{"name":"迪迪","age":"5"}}

  1. eclipse的自动完成的快捷键是 输入字母后按”ALT”+’/’

  2. 切换配置文件 添加 4 个配置文件：application.yml：默认配置

  3. application-dev.yml：开发环境配置

  4. application-test.yml：测试环境配置
  5. application-prod.yml：生产环境配置

在application.yml加上下面这段,切换到prod环境 Log会显示 c.f.helloworld.HelloworldApplication : The following profiles are active: prod

spring:
#切换配置
 profiles:
  active: prod #激活开发环境配置

Maven 打包成jar包后(Maven Clean,Maven install),可以用命令行参数 –spring.profiles.active=dev 来指定版本

C:\\spring-boot-study-helloworld\target>java -jar helloworld-0.0.1-SNAPSHOT.jar --spring.profiles.active=dev

打包生成2个文件

.jar.original 是普通jar包，不包含依赖
.jar 是可执行jar包，包含了pom中的所有依赖，可以直接用java -jar 命令执行
如果是部署，就用.jar
如果是给别的项目用，就要给.jar.original这个包

  1. maven 安装dockerfile-maven-plugin ,可以指定image的名字,tag, 直接打包成docker Image, 根目录有Dockerfile和docker-compose.yml, maven build就能自动打包并上传到dockerHub(前提是你注册登录了账号)

docker run -p 8080:8080 ostock/licensing-service:0.0.1-SNAPSHOT

  1. 强大的lombok注解@Getter @Setter@ToString

  2. Maven的仓库地址是。http://mvnrepository.com/ 比如我们要安装某个jar包, 到这个网址查找,它有一段dependency的代码,复制到POM.xml里就可以了, 参考这个

Maven 下载地址要改成阿里云的, 在这个目录新建一个文件 c:\users[用户名]..m2\setting.xml ,写如下的内容. 不然下载太慢了.我update一下要半个小时

xml version="1.0" encoding="UTF-8"?>

<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">

<pluginGroups>
pluginGroups>

<proxies>
proxies>

<servers>
servers>

<mirrors>
<mirror>
<id>aliyunid>
<name>aliyun Mavenname>
<mirrorOf>*mirrorOf>
<url>https://maven.aliyun.com/repository/public/url>
mirror>
mirrors>

<profiles>
profiles>

<activeProfiles>
activeProfiles>
settings>

@PostMapping() 注解这样写,会出现 405错误 方法不被允许 (Method not allowed)

要写成@PostMapping, 或者@PostMapping(“xxxxx”)

@RequestBody最多只能有一个，而@RequestParam()可以有多个。
前端传递如果是 json 格式的数据，不是Form, 我们要传入的参数是一个对象，那就必须使用 @RequestBody。

  • In Spring MVC, “request parameters” map to query parameters, form data, and parts in multipart requests. This is because the Servlet API combines query parameters and form data into a single map called “parameters”, and that includes automatic parsing of the request body.

Eclipse 快速找到类对应的包名, 要点[Link with Editor]

Spring Boot FAQ

Java String转Date new SimpleDateFormat (“yyyy-MM-dd HH:mm:ss”).parse (“2019-01-03 10:59:27”)

CRUD RESTful 测试

package com.example.springdemo;

import static org.assertj.core.api.AssertionsForClassTypes.assertThat;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import org.junit.jupiter.api.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.web.client.TestRestTemplate;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.util.Assert;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;

import com.example.springdemo.model.User;

@SpringBootTest(classes = DemoApplication.class, webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class UserControllerTest {
    @Autowired
    private TestRestTemplate template;
    private final Logger logger = LoggerFactory.getLogger(UserControllerTest.class);

    private int GetAllUser() throws Exception
    {
            String url ="/api/user/users";
              ResponseEntity response = template.getForEntity(url, String.class);
            HttpStatus statusCode = response.getStatusCode();
            assertThat(statusCode).isEqualTo(HttpStatus.OK);

            JSONArray users = new JSONArray(response.getBody());
            int prevCnt = users.length();

            logger.info(users.length()+" user records");
            return prevCnt;
    }
    @Test
    public void CRUD_ok() throws Exception {

        //先查原来有多少个记录
        int prevCnt =GetAllUser();
        assertThat(prevCnt).isGreaterThanOrEqualTo(1);

        //增加一个
        String url = "/api/user/";
        HttpHeaders headers = new HttpHeaders();
        MediaType type = MediaType.APPLICATION_JSON;
        headers.setContentType(type);
        headers.add("Accept", MediaType.APPLICATION_JSON.toString());

        // Object user = new User(9999,"JUnit Test","123456",new SimpleDateFormat("yyyy-MM-dd").parse("2022-2-1"),1);
        Map requestBody = new HashMap();

        requestBody.put("id", "9999");
        requestBody.put("userName", "123");
        requestBody.put("password", "123456");
        requestBody.put("sex", "1");
        HttpEntity> requestEntity = new HttpEntity>(requestBody, headers);
        ResponseEntity response= template.postForEntity(url, requestEntity,String.class);
        HttpStatus statusCode = response.getStatusCode();
        assertThat(statusCode).isEqualTo(HttpStatus.OK);
        int postCnt =GetAllUser();
        assertThat(postCnt).isEqualTo(prevCnt+1);

        //更新内容
        url = "/api/user/9999";
        requestBody.put("userName", "JUnit");
        requestEntity = new HttpEntity>(requestBody, headers);
        response=template.exchange(url,HttpMethod.PUT,requestEntity,String.class);
        statusCode = response.getStatusCode();
        assertThat(statusCode).isEqualTo(HttpStatus.OK);

        //https://blog.csdn.net/justin_bob/article/details/103019115

        //删除内容

        url = "/api/user/9999";
        response=template.exchange(url,HttpMethod.DELETE,requestEntity,String.class);
      //template.delete("api/user/9999");
        statusCode = response.getStatusCode();
        assertThat(statusCode).isEqualTo(HttpStatus.OK);
    }

}

连接别的机器上的kafka,出现下面错误

Connection to node 1 (localhost/127.0.0.1:9092) could not be established. Broker may not be available.

但application.yml配置的不是本地127.0.0.1地址, 这个就要改kafka的 _ advertised<span class="token punctuation">.listeners</span>_

允许外部端口连接
listeners=PLAINTEXT://0.0.0.0:9092
外部代理地址
advertised.listeners=PLAINTEXT://121.201.64.12:9092

Kafka连接服务器出现:Connection to node 1 (localhost/127.0.0.1:9092) could not be establishedSLF4J 多个Binding如何处理？

SLF4J: Class path contains multiple SLF4J bindings.

SLF4J: Found binding in [jar:file:/C:/Users/user/.m2/repository/ch/qos/logback/logback-classic/1.2.11/logback-classic-1.2.11.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/C:/Users/user/.m2/repository/org/slf4j/slf4j-reload4j/1.7.36/slf4j-reload4j-1.7.36.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.

SLF4J: Actual binding is of type [ch.qos.logback.classic.util.ContextSelectorStaticBinder]

某个项目假如要去掉kafka send/listen的功能，又暂时保留文件，可以用排除功能，把kafka开头的文件都排除在编译之外

Spring Boot FAQ

Q: 没有为模块main指定输出路径

Spring Boot FAQ

Q: 管理依赖库升级

Spring Boot FAQ

Original: https://www.cnblogs.com/zitjubiz/p/15841931.html
Author: Gu
Title: Spring Boot FAQ

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