Spring Boot Guides Examples(1~3)

参考网址：https://spring.io/guides

创建一个RESTful Web Service

• 使用Eclipse 创建一个 Spring Boot项目

Project -> Other -> Spring Boot -> Spring Starter Project

• 直接找到，spring boot自动创建的application类，

#我的是 RestfulWebService1Application.java
右键 -> Run As -> Java Application 运行
------------------console result---------------------
#看见下面两行，则开启成功
2019-02-24 10:38:42.935  INFO 6724 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2019-02-24 10:38:42.940  INFO 6724 --- [           main] c.e.kane.RestfulWebService1Application   : Started RestfulWebService1Application in 4.108 seconds (JVM running for 5.631)

• 打开浏览器，键入 localhost:8080会得到下面的报错信息，因为我们还没有定义Controller

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.Sun Feb 24 10:39:50 CST 2019
There was an unexpected error (type=Not Found, status=404).
No message available
## 可以参考下面的网址，对Whitelabel Error Page 自定义
https://www.baeldung.com/spring-boot-custom-error-page

注：可以自定义该页面，到官网查看

• 开始写如一些java类

// 在Application同级目录下创建Model 文件夹，增加Greeting 类
// Greeting.java
package com.example.kane.Model;
public class Greeting{private final long id;private final String content;public Greeting (long id , String content){this.id = id ;this.content = content;}public long getId(){return id;}public String getContent(){return content;}
}
// 在Application同级目录下创建 Controller文件夹，增加GreetingController
// GreetingController.java
package com.example.kane.Controller;import java.util.concurrent.atomic.AtomicLong;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;// RestController是Spring4的新的注解，被注解的controller返回域对象，不是view// 它是@Controller和@ResponseBody的缩写
import org.springframework.web.bind.annotation.RestController;
import com.example.kane.Model.*;
@RestController
public class GreetingController {private static final String template = "Hello, %s!";private final AtomicLong counter = new AtomicLong();@RequestMapping("/greeting")public Greeting greeting(@RequestParam(value="name", defaultValue="World") String name) {return new Greeting(counter.incrementAndGet(),String.format(template, name));}
}

• 访问 localhost:8080/greeting

# 页面结果
{"id":1,"content":"Hello, World!"}

• 至此一个简单的Restful Web Service 搭好了

注：官方的关于Restful Web Service 网址 https://spring.io/guides/gs/rest-service/

创建一个计划的任务 Scheduling Tasks

• 创建schdule task类

package com.example.kane;
import java.text.SimpleDateFormat;
import java.util.Date;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;
@Componentpublic class SchduleTask {private static final Logger log = LoggerFactory.getLogger(SchduleTask.class);private static final SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");@Scheduled(fixedRate = 5000)public void reportCurrentTime() {log.info("The time is now {}", dateFormat.format(new Date()));}
}

• 更改Application 类，增加@EnableScheduling

package com.example.kane;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableScheduling;
@SpringBootApplication
@EnableScheduling
public class RestfulWebService1Application {public static void main(String[] args) {SpringApplication.run(RestfulWebService1Application.class, args);}}

• 结果，会在console中看到如下输出

2019-02-24 12:00:14.770  INFO 21096 --- [   scheduling-1] com.example.kane.SchduleTask             : The time is now 12:00:14
2019-02-24 12:00:19.770  INFO 21096 --- [   scheduling-1] com.example.kane.SchduleTask             : The time is now 12:00:19
2019-02-24 12:00:24.770  INFO 21096 --- [   scheduling-1] com.example.kane.SchduleTask             : The time is now 12:00:24## 不停地运行Schdule函数

• 其他的Schdule选项

https://docs.spring.io/spring/docs/current/spring-framework-reference/integration.html#scheduling

// 等待上一个执行之后5秒执行下一次
@Scheduled(fixedDelay=5000)
//-------------------------------------
//上一次开启之后5秒执行下一次，无论第一次是否执行完成
@Scheduled(fixedRate = 5000)
//-------------------------------------
// 使用cron 进行定时的安排，语法与linux cronjob相同
@Scheduled(cron="*/5 * * * * MON-FRI")

注：cron表达式规则

Seconds Minutes Hours DayofMonth Month DayofWeek Year
或
Seconds Minutes Hours DayofMonth Month DayofWeek

字段	允许值	允许的特殊字符
秒（Seconds）	0~59的整数	, - * / 四个字符
分（Minutes）	0~59的整数	, - * / 四个字符
小时（Hours）	0~23的整数	, - * / 四个字符
日期（DayofMonth）	1~31的整数（但是你需要考虑你月的天数）	,- * ? / L W C 八个字符
月份（Month）	1~12的整数或者 JAN-DEC	, - * / 四个字符
星期（DayofWeek）	1~7的整数或者 SUN-SAT （1=SUN）	, - * ? / L C # 八个字符
年(可选，留空)（Year）	1970~2099	, - * / 四个字符

## 消费一个Restful Web Service

这里的消费意为在java中访问一些Restful API 并获得想要的内容。

• 更改 Application.java文件

package com.example.kane;import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.scheduling.annotation.EnableScheduling;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.client.RestTemplate;@SpringBootApplication
public class RestfulWebService1Application {private static final Logger log = LoggerFactory.getLogger(RestfulWebService1Application.class);public static void main(String[] args) {
//      不启动Spring boot的application，直接运行RestTemplate
//      SpringApplication.run(RestfulWebService1Application.class, args);RestTemplate restTemplate = new RestTemplate();System.out.println(Quote.class);Quote quote = restTemplate.getForObject("http://gturnquist-quoters.cfapps.io/api/random", Quote.class);log.info(quote.toString());}/*  下面的代码官方说明是要管理RestTemplate，不明白什么意思@Beanpublic RestTemplate restTemplate(RestTemplateBuilder builder) {return builder.build();}@Beanpublic CommandLineRunner run(RestTemplate restTemplate) throws Exception {return args -> {Quote quote = restTemplate.getForObject("http://gturnquist-quoters.cfapps.io/api/random", Quote.class);log.info(quote.toString());};}*/
}

• 定义一个Quote.java类

// Quote 定义的时候需要知道 restful api 返回的json对象都有什么属性，如果Quote中定义的属性在api中不存在那么将被复制为null，
//我将官网的type属性更改为 type1属性后，结构显示type1:null
package com.example.kane;import com.fasterxml.jackson.annotation.JsonIgnoreProperties;@JsonIgnoreProperties(ignoreUnknown = true)
public class Quote {private String type1;private Value value;public Quote() {}public String getType() {return type1;}public void setType(String type) {this.type1 = type;}public Value getValue() {return value;}public void setValue(Value value) {this.value = value;}@Overridepublic String toString() {return "Quote{" +"type='" + type1 + '\'' +", value=" + value +'}';}
}

• 定义Value.java

//value 与 quote相同，定义了这两个类 主要是http://gturnquist-quoters.cfapps.io/api/random返回的json对象中有这两个类
package com.example.kane;import com.fasterxml.jackson.annotation.JsonIgnoreProperties;@JsonIgnoreProperties(ignoreUnknown = true)
public class Value {private Long id;private String quote;public Value() {}public Long getId() {return this.id;}public String getQuote() {return this.quote;}public void setId(Long id) {this.id = id;}public void setQuote(String quote) {this.quote = quote;}@Override    public String toString() {return "Value{" +"id=" + id +", quote='" + quote + '\'' +'}';}
}

• 上结果

20:59:39.613 [main] INFO com.example.kane.RestfulWebService1Application - Quote{type='null', value=Value{id=4, quote='Previous to Spring Boot, I remember XML hell, confusing set up, and many hours of frustration.'}}