前言
Spring Boot 提供的restful服务这么方便，那有没有方便的调用方式呢？当然有了那就是RestTemplate
一、什么是RestTemplate
传统情况下在java代码里访问restful服务，一般使用Apache的HttpClient。不过此种方法使用起来太过繁琐。spring提供了一种简单便捷的模板类来进行操作，这就是RestTemplate。
二、启动服务
我们使用前一篇文章《架构实战篇（五）：Spring Boot 表单验证和异常处理》做服务端提供服务
启动完毕后访问
http://localhost:8081/swagger/swagger-ui.html
测试服务是否启动正常
三、Java 客户端
让我们先来看下项目的目录结构
目录结构
四、配置maven依赖
<?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.itunion</groupId> <artifactId>spring-boot-resttemplate</artifactId> <version>1.0-SNAPSHOT</version> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.5.1.RELEASE</version> </parent> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>io.springfox</groupId> <artifactId>springfox-swagger2</artifactId> <version>2.7.0</version> </dependency> <dependency> <groupId>io.springfox</groupId> <artifactId>springfox-swagger-ui</artifactId> <version>2.7.0</version> </dependency> <dependency> <groupId>org.apache.tomcat.embed</groupId> <artifactId>tomcat-embed-jasper</artifactId> </dependency> <!-- 打war包用 --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> <scope>provided</scope> </dependency> </dependencies> <packaging>war</packaging> <properties> <java.version>1.7</java.version> </properties> <build> <!-- 打war包用 --> <finalName>swagger</finalName> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> <!-- 打war包用,maven打包的时候告诉maven不需要web.xml,否刚会报找不到web.xml错误 --> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-war-plugin</artifactId> <version>2.1.1</version> <configuration> <failOnMissingWebXml>false</failOnMissingWebXml> </configuration> </plugin> <!-- --> </plugins> </build></project>
五、编写程序入口
程序的入口基本都一样
package com.itunion;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import java.io.IOException;
@SpringBootApplication
public class Application {
public static void main(String[] args) throws IOException {
SpringApplication.run(Application.class, args);
}
}六、RestTemplate 配置
在这里我们可以设置连接的超时时间 代理 等信息
package com.itunion.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.ClientHttpRequestFactory;
import org.springframework.http.client.SimpleClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;@Configuration
public class ApiConfig {
@Bean
public RestTemplate restTemplate(ClientHttpRequestFactory factory) { return new RestTemplate(factory);
}
@Bean
public ClientHttpRequestFactory simpleClientHttpRequestFactory() {
SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
factory.setReadTimeout(5000);//单位为ms
factory.setConnectTimeout(5000);//单位为ms
return factory;
}
}七、编写API 返回对象
API 请求肯定少不了返回对象，为了方便类型转换我们把User类复制了过来（实际开发中可以把api 公共的domain 等类带jar 包出来)
package com.itunion.model;
import com.fasterxml.jackson.annotation.JsonIgnore;
import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
@ApiModel("用户")
public class User {
@ApiModelProperty("编号")
private Long id;
@ApiModelProperty("用户名")
private String username;
@ApiModelProperty("姓")
private String firstName;
@ApiModelProperty("名")
private String lastName;
@ApiModelProperty("邮箱")
private String email;
@ApiModelProperty(hidden = true)// 密码不传输
@JsonIgnore
private String password;
@ApiModelProperty("状态")
private Integer userStatus; // get set
@Override
public String toString() {
return "User{" + "id=" + id + ", username='" + username + '\'' + ", firstName='" + firstName + '\'' + ", lastName='" + lastName + '\'' + ", email='" + email + '\'' + ", password='" + password + '\'' + ", userStatus=" + userStatus + '}';
}
}异常类
package com.itunion.model;
import java.o.Serializable;
public class ErrorBody implements Serializable {
private Integer code;
private String message;
private long timestamp = System.currentTimeMillis();
// get set
@Override
public String toString() {
return "ErrorBody{" + "code=" + code + ", message='" + message + '\'' + ", timestamp=" + timestamp + '}';
}
}八、使用RestTemplate 远程调用
这里我们写了两个方法
当远程接口正常返回结果的时候我们会封装成User对象返回到前端
当远程调用返回 RestClientResponseException 异常的时候封装成ErrorBody对象(比如传入参数不合法等数据验证，不能返回逾期结果的时候会返回Error信息，这时候需要做处理)
package com.itunion.controller;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.itunion.model.ErrorBody;
import com.itunion.model.User;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.HttpClientErrorException;
import org.springframework.web.client.RestTemplate;
import java.io.IOException;@Api(value = "用户", description = "用户")
@RequestMapping("/user")@RestController
public class UserController {
@Autowired
private RestTemplate restTemplate;
@ApiOperation(value = "调用远程用户服务", notes = "调用远程用户服务")
@RequestMapping(value = "/info/{userId}", method = RequestMethod.GET)
public User info(@PathVariable("userId") String userId) throws IOException {
String apiURL = "http://localhost:8081/swagger/user/info/" + userId;
return restTemplate.getForObject(apiURL, User.class);
}
@ExceptionHandler(RestClientResponseException.class)
public ErrorBody exceptionHandler(HttpClientErrorException e) throws IOException {
return new ObjectMapper().readValue(e.getResponseBodyAsString(), ErrorBody.class);
}
}九、修改端口
为了同时启动两个服务端口肯定是不能一样的了
server.port=8082 server.context-path=/ swagger.enable=true
十、启动程序和验证
服务端成功启动
服务端成功启动
客户端成功启动
客户端成功启动
访问客户端页面
http://localhost:8082/swagger-ui.html
测试正确的请求参数
设置参数
验证正确结果
测试错误的请求参数
设置参数
验证异常结果
好了 RestTemplate 的简单实用就到这里了
