springboot学习总结（三）RestTemplate用法

（一）配置类

package com.vincent.demo.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 RestTemplateConfig {

    @Bean
    public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
        return new RestTemplate(factory);
    }

    @Bean
    public ClientHttpRequestFactory simpleClientHttpRequestFactory() {
        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
        factory.setReadTimeout(5000);
        factory.setConnectTimeout(15000);
        return factory;
    }
}

（二）准备的VO类

package com.vincent.demo.vo;

public class TestVO {

    private Long id;

    private String name;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "TestVO{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}

（三）get请求

1、getForObject

官方提供了如下三个方法

（1）public <T> T getForObject(URI url, Class<T> responseType) throws RestClientException {}

（2）public <T> T getForObject(String url, Class<T> responseType, Object... uriVariables) throws RestClientException {}

（3）public <T> T getForObject(String url, Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException {}

（1）无參get请求

controller方法如下

    @GetMapping("/getTest")
    public String getTest() {
        return "getTest";
    }

测试方法

String msg = restTemplate.getForObject("http://localhost:8080/getTest", String.class);
System.out.println(msg);

控制台打印信息：

getTest

（2）有参数的get请求

controller方法：

    @GetMapping("/urlWithParam/{id}/{name}")
    public String urlWithParam(@PathVariable Long id, @PathVariable String name) {
        return "id:" + id + ",name:" + name;
    }

测试方法：

String msg1 = restTemplate.getForObject("http://localhost:8080/urlWithParam/{id}/{name}", String.class, 1, "vincent");
System.out.println(msg1);

控制台打印信息：

id:1,name:vincent

（3）有参数的get请求

controller方法：

    @GetMapping("/getWithVo")
    public String getWithVo(TestVO testVO) {
        return testVO.toString();
    }

测试方法：

        Map<String, String> map = new HashMap();
        map.put("id", "1");
        map.put("name", "vincent");
        String msg2 = restTemplate.getForObject("http://localhost:8080/urlWithParam/{id}/{name}", String.class, map);
        System.out.println("msg2:" + msg2);

控制台打印信息：

msg2:id:1,name:vincent

（四）有参数的get请求

这一种的情况个人认为比较特殊，用的是无參的<T> T getForObject(URI url, Class<T> responseType)，也许是我没找到合适的方式来调用，后期找到了再更新

controller方法：

    @GetMapping("/getWithParam")
    public String getWithParam(@RequestParam Long id, @RequestParam String name) {
        return "id:" + id + ",name:" + name;
    }

测试方法：

        String msg3 = restTemplate.getForObject("http://localhost:8080/getWithParam?id=1&name=vincent", String.class);
        System.out.println("msg3:" + msg3);

控制台打印信息：

msg3:id:1,name:vincent

2、getForEntity

官方提供了如下方法：

    public <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Object... uriVariables) throws RestClientException {}

    public <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException {}

    public <T> ResponseEntity<T> getForEntity(URI url, Class<T> responseType) throws RestClientException {}

除了返回类型，基本和getForObject一样。

这边举一个无參的请求作为例子

controller方法：

    @GetMapping("/getTest")
    public String getTest() {
        return "getTest";
    }

测试方法：

        ResponseEntity<String> entity = restTemplate.getForEntity("http://localhost:8080/getTest", String.class);
        System.out.println("body:" + entity.getBody()
                + ",StatusCode:" + entity.getStatusCode()
                + ",StatusCodeValue:" + entity.getStatusCodeValue()
                + ",:Headers" + entity.getHeaders());

控制台打印：

body:getTest,StatusCode:200,StatusCodeValue:200,:Headers{Content-Type=[text/plain;charset=UTF-8], Content-Length=[7], Date=[Wed, 09 Jan 2019 15:09:04 GMT]}

小结：

getForEntity和getForObject的区别其实就在于返回值，getForEntity的返回值包含http的一些信息，而getForObject就只有接口返回的信息。
这一点看他的源码很容易明白

    public <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Object... uriVariables) throws RestClientException {
        RequestCallback requestCallback = this.acceptHeaderRequestCallback(responseType);
        ResponseExtractor<ResponseEntity<T>> responseExtractor = this.responseEntityExtractor(responseType);
        return (ResponseEntity)this.execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);
    }

    public <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException {
        RequestCallback requestCallback = this.acceptHeaderRequestCallback(responseType);
        ResponseExtractor<ResponseEntity<T>> responseExtractor = this.responseEntityExtractor(responseType);
        return (ResponseEntity)this.execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);
    }

    public <T> ResponseEntity<T> getForEntity(URI url, Class<T> responseType) throws RestClientException {
        RequestCallback requestCallback = this.acceptHeaderRequestCallback(responseType);
        ResponseExtractor<ResponseEntity<T>> responseExtractor = this.responseEntityExtractor(responseType);
        return (ResponseEntity)this.execute(url, HttpMethod.GET, requestCallback, responseExtractor);
    }

    public <T> T getForObject(String url, Class<T> responseType, Object... uriVariables) throws RestClientException {
        RequestCallback requestCallback = this.acceptHeaderRequestCallback(responseType);
        HttpMessageConverterExtractor<T> responseExtractor = new HttpMessageConverterExtractor(responseType, this.getMessageConverters(), this.logger);
        return this.execute(url, HttpMethod.GET, requestCallback, responseExtractor, (Object[])uriVariables);
    }

    public <T> T getForObject(String url, Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException {
        RequestCallback requestCallback = this.acceptHeaderRequestCallback(responseType);
        HttpMessageConverterExtractor<T> responseExtractor = new HttpMessageConverterExtractor(responseType, this.getMessageConverters(), this.logger);
        return this.execute(url, HttpMethod.GET, requestCallback, responseExtractor, (Map)uriVariables);
    }
    public <T> T getForObject(URI url, Class<T> responseType) throws RestClientException {
        RequestCallback requestCallback = this.acceptHeaderRequestCallback(responseType);
        HttpMessageConverterExtractor<T> responseExtractor = new HttpMessageConverterExtractor(responseType, this.getMessageConverters(), this.logger);
        return this.execute(url, HttpMethod.GET, requestCallback, responseExtractor);
    }

三类方法调用对应的execute(）方法

    public <T> T execute(String url, HttpMethod method, RequestCallback requestCallback, ResponseExtractor<T> responseExtractor, Object... uriVariables) throws RestClientException {
        URI expanded = this.getUriTemplateHandler().expand(url, uriVariables);
        return this.doExecute(expanded, method, requestCallback, responseExtractor);
    }

    public <T> T execute(String url, HttpMethod method, RequestCallback requestCallback, ResponseExtractor<T> responseExtractor, Map<String, ?> uriVariables) throws RestClientException {
        URI expanded = this.getUriTemplateHandler().expand(url, uriVariables);
        return this.doExecute(expanded, method, requestCallback, responseExtractor);
    }

    public <T> T execute(URI url, HttpMethod method, RequestCallback requestCallback, ResponseExtractor<T> responseExtractor) throws RestClientException {
        return this.doExecute(url, method, requestCallback, responseExtractor);
    }

execute(）方法最终都调用的是doExecute(url, method, requestCallback, responseExtractor)；

所以getForEntity和getForObject的区别就是responseExtractor用的是不同的实现