Consuming a RESTful Web Service

---

这个Demo是用来演示使用Restful Web Service的。官网参考文献

一、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-consuming-rest</artifactId>
    <version>0.1.0</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.5.RELEASE</version>
    </parent>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
        </dependency>
    </dependencies>


    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

使用Spring Boot Maven plugin是为了利用它的自动寻找Main方法和可以将应用所依赖的所有包打包为一个可以运行的jar。

二、创建一些类来存储获取的数据

访问链接 http://gturnquist-quoters.cfapps.io/api/random，将获得随机数据

{"type":"success","value":{"id":11,"quote":"I have two hours today to build an app from scratch. @springboot to the rescue!"}}

我们用两个类来承接这个数据

package hello;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown = true)
public class Quote {

    private String type;
    private Value value;

    public Quote() {
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public Value getValue() {
        return value;
    }

    public void setValue(Value value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "Quote{" +
                "type='" + type + '\'' +
                ", value=" + value +
                '}';
    }
}

package hello;

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 + '\'' +
                '}';
    }
}

其中JsonIgnoreProperties的作用是，当获取的json数据的属性名与我们类的属性名不匹配时 忽视 它。

三、启动

启动获取数据我们通过普通的main方法就行了。但是我们也可以让springboot来管理应用的生命周期。好处是可以让springboot将json转换为相应的对象。

package hello;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
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.web.client.RestTemplate;

@SpringBootApplication
public class Application {

	private static final Logger log = LoggerFactory.getLogger(Application.class);

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

	@Bean
	public RestTemplate restTemplate(RestTemplateBuilder builder) {
		return builder.build();
	}

	@Bean
	public 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());
		};
	}
}

将RestTemplate移到CommandLineRunner去是为了让json的解析发生在spirngboot启动项目之前运行。RestTemplateBuilder是被springboot自动注入的，如果使用RestTemplateBuilder产生RestTemplate，将得到springboot自动配置的好处（比如将json转换）。