RestTemplate GET 请求详解

getForEntity

getForEntity(String url, Class responseType, Object… urlVariables)

url ： 请求的地址
responseType : 响应体 body 的包装类型
urlVariables ： 参数数组，用于替换 url 中占位符对用的参数

@RequestMapping(value = "/get-for-entity-01")
public String getForEntity01() {
    ResponseEntity<String> responseEntity =
        restTemplate.getForEntity(
            "http://DEMO-REST-TEMPLATE-PROVIDER-EUREKA-CLIENT/user/name?userId=1",
            String.class);
    return responseEntity.getBody();
}

而使用参数数组的方式需要在url中指定占位符，占位符中的顺序即参数在数组中的索引：

@RequestMapping(value = "/get-for-entity-02")
public String getForEntity02() {
    ResponseEntity<String> responseEntity =
        restTemplate.getForEntity(
            "http://DEMO-REST-TEMPLATE-PROVIDER-EUREKA-CLIENT/user/name?userId={1}",
            String.class,
            "1");
    return responseEntity.getBody();
}

支持字符串方式返回响应对象体：

@RequestMapping(value = "/get-for-entity-03")
public String getForEntity03() {
    ResponseEntity<String> responseEntity =
        restTemplate.getForEntity(
            "http://DEMO-REST-TEMPLATE-PROVIDER-EUREKA-CLIENT/user?userId={1}",
            String.class,
            "1");
    return responseEntity.getBody();
}

支持对象方式返回响应体（SpringMVC 会将对象序列化为JSON）：

@RequestMapping(value = "/get-for-entity-04")
public User getForEntity04() {
    ResponseEntity<User> responseEntity =
        restTemplate.getForEntity(
            "http://DEMO-REST-TEMPLATE-PROVIDER-EUREKA-CLIENT/user?userId={1}",
            User.class,
            "1");
    return responseEntity.getBody();
}

getForEntity(String url, Class responseType, Map urlVariables)

该方式是将请求参数封装进 Map ：

@RequestMapping(value = "/get-for-entity-05")
public String getForEntity05() {
    Map<String, String> params = new HashMap<>(8);
    params.put("userId", "1");
    ResponseEntity<String> responseEntity =
        restTemplate.getForEntity(
            "http://DEMO-REST-TEMPLATE-PROVIDER-EUREKA-CLIENT/user/name?userId={userId}",
            String.class,
            params);
    return responseEntity.getBody();
}

getForEntity(URI uri, Class responseType)

该方式是以构建URI的方式传递请求参数：

@RequestMapping(value = "/get-for-entity-06")
public String getForEntity06() {
    UriComponents uriComponents = UriComponentsBuilder.fromUriString(
        "http://DEMO-REST-TEMPLATE-PROVIDER-EUREKA-CLIENT/user/name?userId={userId}")
        .build()
        .expand("1")
        .encode();
    URI uri = uriComponents.toUri();
    ResponseEntity<String> responseEntity = restTemplate.getForEntity(uri, String.class);
    return responseEntity.getBody();
}

getForObject

getForObject 是对 getForEntity 的进一步封装，自动对请求响应 body 内容进行对象转换。

getForObject(String url, Class responseType, Object… urlVariables)

@RequestMapping(value = "/get-for-object-01")
public String getForObject01() {
    String userName =
        restTemplate.getForObject(
            "http://DEMO-REST-TEMPLATE-PROVIDER-EUREKA-CLIENT/user/name?userId={1}",
            String.class,
            "1");
    return userName;
}

getForObject(String url, Class responseType, Map urlVariables)

@RequestMapping(value = "/get-for-object-02")
public String getForObject02() {
    Map<String, String> params = new HashMap<>(8);
    params.put("userId", "1");
    String userName =
        restTemplate.getForObject(
            "http://DEMO-REST-TEMPLATE-PROVIDER-EUREKA-CLIENT/user/name?userId={userId}",
            String.class,
            params);
    return userName;
}

getForObject(URI url, Class responseType)

@RequestMapping(value = "/get-for-object-03")
public String getForObject03() {
    UriComponents uriComponents = UriComponentsBuilder.fromUriString(
        "http://DEMO-REST-TEMPLATE-PROVIDER-EUREKA-CLIENT/user/name?userId={userId}")
        .build()
        .expand("1")
        .encode();
    URI uri = uriComponents.toUri();
    String userName = restTemplate.getForObject(uri, String.class);
    return userName;
}

一般直接在 url 中组合参数或者使用 getForObject(String url, Class responseType, Map urlVariables)

赏

谢谢你请我吃糖果