SpringCloud 学习(7)：第一个Feign

红太狼 2020-11-15 15:41 726阅读 0赞

## 一、简介 ##

Feign是一个声明性的Web服务客户端。 它使编写Web服务客户端变得更容易。 
要使用Feign，请创建一个界面并对其进行注释。 它具有可插入的注释支持，
包括Feign注释和JAX-RS注释。 Feign还支持可插拔编码器和解码器。
简单的说Feign就是一个restful客户端。

## 二、Feign hello world ##

这篇文章主要通过写一个简单Feign程序，来了解一下Feign的原理。

![这里写图片描述][70]

项目非常简单，通过feign-service提供3个接口，通过feign-client 对接口进行访问。  
废话不多说，直接上代码：

--------------------

## 一、feign-service ##

*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>com.warrior</groupId>
        <artifactId>feign-service</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <dependencies>
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
                <version>2.0.0.RELEASE</version>
            </dependency>
            
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>fastjson</artifactId>
                <version>1.2.46</version>
            </dependency>
        </dependencies>
    </project>
````
*Application.java
````
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    /**
     * @author: lqh
     * @description:
     * @program: feign-service
     * @create: 2018-07-02 10:25
     **/
    @SpringBootApplication
    public class Application {
        public static void main(String[] args) {
            SpringApplication.run(Application.class, args);
        }
    }
````
*application.properties
````
    server.port = 2001
````
*Person.java
````
    public class Person {
        private Integer id;
        private Integer age;
        private String name;
    
        public Integer getId() {
            return id;
        }
    
        public Person setId(Integer id) {
            this.id = id;
            return this;
        }
    
        public Integer getAge() {
            return age;
        }
    
        public Person setAge(Integer age) {
            this.age = age;
            return this;
        }
    
        public String getName() {
            return name;
        }
    
        public Person setName(String name) {
            this.name = name;
            return this;
        }
    }
````
*PersonController.java
````
    import com.alibaba.fastjson.JSON;
    import org.springframework.web.bind.annotation.*;
     
    @RestController
    public class PersonController {
    
        @RequestMapping("hello")
        public String hello(){
            return "hello world.";
        }
    
        @RequestMapping("getPerson")
        public String hello(@RequestParam("id") Integer id){
            Person person = new Person();
            person.setId(id);
            person.setAge(23);
            person.setName("warrior");
            return JSON.toJSONString(person);
        }
    
        @PostMapping("insertPerson")
        public String insertPerson(@RequestBody Person person){
            return person.getName();
        }
    }
````
--------------------

## 二、feign-client ##

*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>com.warrior</groupId>
        <artifactId>feign-client</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <dependencies>
            <dependency>
                <groupId>io.github.openfeign</groupId>
                <artifactId>feign-core</artifactId>
                <version>9.5.0</version>
            </dependency>
            <dependency>
                <groupId>io.github.openfeign</groupId>
                <artifactId>feign-gson</artifactId>
                <version>9.5.0</version>
            </dependency>
        </dependencies>
    </project>
````
*Person.java
````
    public class Person {
        private Integer id;
        private Integer age;
        private String name;
    
        public Integer getId() {
            return id;
        }
    
        public Person setId(Integer id) {
            this.id = id;
            return this;
        }
    
        public Integer getAge() {
            return age;
        }
    
        public Person setAge(Integer age) {
            this.age = age;
            return this;
        }
    
        public String getName() {
            return name;
        }
    
        public Person setName(String name) {
            this.name = name;
            return this;
        }
    }
````
*FeignClient.java
````
    import feign.Headers;
    import feign.Param;
    import feign.RequestLine;
    
    public interface FeignClient {
        @RequestLine("GET /hello") //指定请求方式 uri
        String hello();
    
        @RequestLine("GET /getPerson?id={id}") //有参数的格式
        Person getPerson(@Param("id") Integer id);
    
        @RequestLine("POST /insertPerson")
        @Headers("Content-Type: application/json") //指定参数为json格式
        public String insertPerson(Person person);
    }
````
*FeignTest.java
````
    import com.google.gson.Gson;
    import feign.Feign;
    import feign.gson.GsonDecoder;
    import feign.gson.GsonEncoder;
     
    public class FeignTest {
        public static void main(String[] args) {
            //1.无参
    /*        FeignClient feignClient = Feign.builder()
                    .target(FeignClient.class, "http://localhost:2001");
            String res = feignClient.hello();
            System.out.println("res:" + res);*/
    
            //2.使用解码器
    /*        FeignClient feignClient = Feign.builder()
                    .decoder(new GsonDecoder())
                    .target(FeignClient.class, "http://localhost:2001");
            Person person = feignClient.getPerson(1);
            System.out.println("person:" + person.getName());*/
    
            //3.使用编码器
            FeignClient client = Feign.builder().encoder(new GsonEncoder())
                    .target(FeignClient.class, "http://localhost:2001");
            Person person = new Person();
            person.setId(1);
            person.setAge(22);
            person.setName("warrior");
            String res = client.insertPerson(person);
            System.out.println(res);
        }
    }
````
--------------------

三、自定义请求拦截器 ：  
修改feign-client项目如下–>  
![这里写图片描述][70 1]

*Feign.java
````
    import com.warrior.Person;
    import feign.Headers;
    import feign.Param;
    import feign.RequestLine;
    
    public interface FeignClient {
        @RequestLine("GET /hello") //指定请求方式 uri
        String hello();
    
        @RequestLine("GET /getPerson?id={id}") //有参数的格式
        Person getPerson(@Param("id") Integer id);
    
        @RequestLine("POST /insertPerson")
        public String insertPerson(Person person);
    }
````
*MyRequestIntercepter.java
````
    import feign.RequestInterceptor;
    import feign.RequestTemplate;
    
     
    public class MyRequestIntercepter implements RequestInterceptor{
        public void apply(RequestTemplate requestTemplate) {
            System.out.println("自定义请求拦截器...............");
            requestTemplate.header("Content-type","application/json");
        }
    }
````
*RequestIntercepterMain.java
````
    import com.warrior.Person;
    import feign.Feign;
    import feign.Logger;
    import feign.gson.GsonEncoder;
    
      
    public class RequestIntercepterMain {
        public static void main(String[] args) {
            FeignClient client = Feign.builder()
                    .requestInterceptor(new MyRequestIntercepter())//设置拦截器
                    .encoder(new GsonEncoder())
                    .logLevel(Logger.Level.FULL) //设置日志级别
                    .logger(new Logger.JavaLogger().appendToFile("logs/xx.log"))//设置日志文件
                    .target(FeignClient.class, "http://localhost:2001");
            Person person = new Person();
            person.setId(1);
            person.setAge(22);
            person.setName("warrior");
            String res = client.insertPerson(person);
            System.out.println(res);
        }
    }
````

[70]: /images/1605454863934.png
[70 1]: /images/1605454887945.png