spring rest template - downgoon/hello-world GitHub Wiki
REST 服务盛行，那么作为客户端如何访问REST服务呢？
最简单的方式用 Apache Http Client 去访问 Web 服务，对返回值用 Jackson 反序列化成 Java 对象。
在 Spring 里面，负责这功能的工具是 RestTemplate， 它的确也是依据上面的原理。
访问在线REST服务，比如 http://example.com/ping.json，返回的JSON是：
{attachment=null, debug=20170119135706172357:系统运行正常, message=成功, status=200}
用 RestTemplate访问：
import java.net.URI;
import java.util.Map;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;
public class RestTemplateExample {
@SuppressWarnings("unchecked")
public static void main(String[] args) throws Exception {
RestTemplate rest = new RestTemplate();
ResponseEntity<Object> response = rest.getForEntity(new URI("http://example.com/ping.json"), Object.class);
System.out.println(response);
HttpStatus status = response.getStatusCode();
HttpHeaders headers = response.getHeaders();
/*
* JSON:
* {attachment=null, debug=20170119135706172357:系统运行正常, message=成功, status=200}
*
* Object:
* java.util.LinkedHashMap
*
* */
Map<String,?> body = (Map<String,?>) response.getBody();
System.out.println("status: " + status);
System.out.println("headers: " + headers);
System.out.println("body: " + body);
System.out.println(body.get("message"));
}
}
主要代码：
RestTemplate rest = new RestTemplate(); ResponseEntity response = rest.getForEntity(new URI("http://example.com/ping.json"), Object.class);
pom 中的依赖：
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.3.3.RELEASE</version>
</parent>
<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-core</artifactId>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
</dependency>
</dependencies>
其中``RestTemplate``位于：
演示需要的代码位于：
$ git checkout spring-rest-template
$ git checkout spring-rest-template-c1-json
指定Body的类型：
RestTemplate rest = new RestTemplate();
ResponseEntity<RestJson> response = rest.getForEntity(new URI("http://example.com/ping.json"), RestJson.class);
按JSON定义的Java类型：
public class RestJson {
/*
* {attachment=null, debug=20170119135706172357:系统运行正常, message=成功, status=200}
* */
private Integer status;
private String message;
private String debug;
private Object attachment;
public Integer getStatus() {
return status;
}
public void setStatus(Integer status) {
this.status = status;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public String getDebug() {
return debug;
}
public void setDebug(String debug) {
this.debug = debug;
}
public Object getAttachment() {
return attachment;
}
public void setAttachment(Object attachment) {
this.attachment = attachment;
}
@Override
public String toString() {
return "RestJson [status=" + status + ", message=" + message + ", debug=" + debug + ", attachment=" + attachment
+ "]";
}
}
演示代码：
$ git checkout spring-rest-template
$ git checkout spring-rest-template-c2-json2obj
marshape 是一家做 API Gateway 的公司。它有客户端Unirest。
进入代码：
$ git checkout spring-rest-template
$ git checkout spring-rest-template-c3-marsharp
pom依赖：
<dependency>
<groupId>com.mashape.unirest</groupId>
<artifactId>unirest-java</artifactId>
<version>1.4.9</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
</dependency>
并且 unirest-java 的HTTP实现都依赖 Apache HttpClient 。
样例代码：
import java.io.IOException;
import org.json.JSONArray;
import org.json.JSONObject;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.JsonNode;
import com.mashape.unirest.http.ObjectMapper;
import com.mashape.unirest.http.Unirest;
public class MarsharpClientExample {
public static void main(String[] args) throws Exception {
String api = "http://example.com/ping.json";
HttpResponse<JsonNode> response = Unirest.get(api).queryString("r", "123456").asJson();
int status = response.getStatus();
System.out.println("http status: " + status);
JsonNode node = response.getBody();
if (node.isArray()) {
JSONArray jsonArray = node.getArray();
System.out.println(jsonArray);
} else {
JSONObject jsonObject = node.getObject();
String message = (String) jsonObject.get("message");
System.out.println(message);
}
/*
* Serialization
* */
Unirest.setObjectMapper(new ObjectMapper() {
private com.fasterxml.jackson.databind.ObjectMapper jacksonObjectMapper
= new com.fasterxml.jackson.databind.ObjectMapper();
public <T> T readValue(String value, Class<T> valueType) {
try {
return jacksonObjectMapper.readValue(value, valueType);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
public String writeValue(Object value) {
try {
return jacksonObjectMapper.writeValueAsString(value);
} catch (JsonProcessingException e) {
throw new RuntimeException(e);
}
}
});
// as object
HttpResponse<RestJson> resp2 = Unirest.get(api)
.queryString("r", "123456")
.asObject(RestJson.class);
System.out.println(resp2.getBody().getMessage());
}
}