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feign是一个声明式的web service客户端，它简化了web服务客户端的编写操作，相对于ribbon+resttemplate的方式，开发者只需通过简单的接口和注解来调用http api。它支持spring mvc注解和jax-rs注解，还支持可插拔式的编码器和解码器。整合了eureka，ribbon和hystrix，具有可插拔、基于注解、负载均衡、服务熔断等一系列便捷功能。
我要评论<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>
<parent>
<groupid>com.cf</groupid>
<artifactid>sc-parent</artifactid>
<version>0.0.1-snapshot</version>
</parent>
<artifactid>sc-consumer-feign</artifactid>
<dependencies>
<dependency>
<groupid>org.springframework.cloud</groupid>
<artifactid>spring-cloud-starter-netflix-eureka-client</artifactid>
</dependency>
<dependency>
<groupid>org.springframework.cloud</groupid>
<artifactid>spring-cloud-starter-openfeign</artifactid>
</dependency>
</dependencies>
</project>
package feign;
import org.springframework.boot.springapplication;
import org.springframework.boot.autoconfigure.springbootapplication;
import org.springframework.cloud.openfeign.enablefeignclients;
@springbootapplication
@enablefeignclients
public class feignapplication {
public static void main(string[] args) {
springapplication.run(feignapplication.class, args);
}
}
package feign.inter;
import org.springframework.cloud.openfeign.feignclient;
import org.springframework.web.bind.annotation.getmapping;
@feignclient("sc-provider")
public interface bookservice {
@getmapping("/book/list")
public string getbooklist();
}
package provider.controller;
import org.springframework.web.bind.annotation.getmapping;
import org.springframework.web.bind.annotation.requestmapping;
import org.springframework.web.bind.annotation.restcontroller;
@requestmapping("/book")
@restcontroller
public class bookcontroller {
@getmapping("/list")
public string getbooklist(){
return "[\"java入门到放弃\",\"c++入门到放弃\",\"python入门到放弃\",\"c入门到放弃\"]";
}
}
server:
port: 8084
spring:
application:
name: sc-consumer-feign
eureka:
client:
registerwitheureka: false
serviceurl:
defaultzone: http://localhost:8080/eureka/
feign基于ribbon实现，也具有ribbon负载均衡的特性，可以将调用的提供者服务换成sc-provider-random(请参照springcloud学习笔记(2)：使用ribbon负载均衡)来测试。
上面例子没有涉及到参数的传递，接下来测试下如何使用feign构造带参数的请求，首先对提供者和消费者做如下更改：
//提供者controller添加了两个参数，并打印到控制台。
@requestmapping("/book")
@restcontroller
public class bookcontroller {
@getmapping("/list")
public string getbooklist(string param1, integer param2){
system.out.println(param1 + ":" + param2);
return "[\"java入门到放弃\",\"c++入门到放弃\",\"python入门到放弃\",\"c入门到放弃\"]";
}
}
//消费者feign接口和controller添加参数
@feignclient("sc-provider")
public interface bookservice {
@getmapping("/book/list")
public string getbooklist(string param1, integer param2);
}
@requestmapping("/feign")
@restcontroller
public class feigncontroller {
@autowired
private bookservice bookservice;
@getmapping("/getbooklist")
public string getbooklist(){
return bookservice.getbooklist("java", 520);
}
}
依次启动注册中心sc-eureka、提供者sc-provider、消费者sc-consumer-feign，启动消费者sc-consumer-feign时会启动失败：
java.lang.illegalstateexception: method has too many body parameters: public abstract java.lang.string feign.inter.bookservice.getbooklist(java.lang.string,java.lang.integer)
更改feign接口，为参数添加@requestparam注解：
@feignclient("sc-provider")
public interface bookservice {
@getmapping("/book/list")
public string getbooklist(@requestparam("param1") string param1, @requestparam("param2") integer param2);
}
将参数封装到map里，更改消费者feign接口和controller：
@feignclient("sc-provider")
public interface bookservice {
@getmapping("/book/list")
public string getbooklist(@requestparam map<string, object> parammap);
}
@requestmapping("/feign")
@restcontroller
public class feigncontroller {
@autowired
private bookservice bookservice;
@getmapping("/getbooklist")
public string getbooklist(){
map<string,object> parammap = new hashmap<string, object>();
parammap.put("param1", "java");
parammap.put("param2", 520);
return bookservice.getbooklist(parammap);
}
}
在参数较多的情况下，该方式可以简化feign接口的编写。
openfeign的@querymap注解支持将自定义类型用于get参数映射，由于@querymap和spring不兼容，spring cloud openfeign提供了一个等价的@springquerymap注解，可以用于自定义类型和map类型的参数映射。下面将使用自定义类型params作为参数，使用@springquerymap注解来处理自定义类型的参数映射。
public class params {
private string param1;
private integer param2;
public string getparam1() {
return param1;
}
public void setparam1(string param1) {
this.param1 = param1;
}
public integer getparam2() {
return param2;
}
public void setparam2(integer param2) {
this.param2 = param2;
}
@override
public string tostring() {
return "params [param1=" + param1 + ", param2=" + param2 + "]";
}
public params(string param1, integer param2) {
this.param1 = param1;
this.param2 = param2;
}
public params() {}
}
//提供者
@requestmapping("/book")
@restcontroller
public class bookcontroller {
@getmapping("/list")
public string getbooklist(params params){
system.out.println(params.tostring());
return "[\"java入门到放弃\",\"c++入门到放弃\",\"python入门到放弃\",\"c入门到放弃\"]";
}
}
//消费者
@feignclient("sc-provider")
public interface bookservice {
@getmapping("/book/list")
public string getbooklist(@springquerymap params params);
}
@requestmapping("/feign")
@restcontroller
public class feigncontroller {
@autowired
private bookservice bookservice;
@getmapping("/getbooklist")
public string getbooklist(){
params params = new params("java", 520);
return bookservice.getbooklist(params);
}
}
params [param1=java, param2=520]
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