RestTemplate

仓库地址：RestTemplate (opens new window)

注入RestTemplate

@Configuration
public class RestTemplateConfig {
    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

GetForEntity方法

package com.cc.resttemplate.controller;

import com.cc.resttemplate.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import java.util.HashMap;
import java.util.Map;

/**
 * @author: lichengcan
 * @date: 2023-12-28 11:27
 * @description GetForEntity
 **/

@RestController
@RequestMapping(value = "/getForEntity")
public class GetForEntityController {

    @Autowired
    RestTemplate restTemplate;

    /**
     * 使用键值对的形式
     */
    @GetMapping("/userKeyValue")
    public User userKeyValue(@RequestParam Long id, @RequestParam String name) {
        return restTemplate.getForEntity("http://localhost:8080/userKeyValue?id={id}&name={name}", User.class, id,name).getBody();
    }

    /**
     * 使用Map的形式
     */
    @GetMapping("/userByMap")
    public User userByMap(@RequestParam Long id, @RequestParam String name) {
        Map<String, Object> requestParams = new HashMap<>(2);
        requestParams.put("id", id);
        requestParams.put("name", name);
        return restTemplate.getForEntity("http://localhost:8080/userKeyValue?id={id}&name={name}", User.class, requestParams).getBody();
    }

    /**
     * 无请求参数
     * @return
     */
    @GetMapping("/userNoRequestParam")
    public User userNoRequestParam() {
        return restTemplate.getForEntity("http://localhost:8080/userKeyValue", User.class).getBody();
    }
}

Exchange方法

package com.cc.resttemplate.controller;

import com.cc.resttemplate.domain.User;
import com.cc.resttemplate.domain.Users;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.RestTemplate;

import java.util.HashMap;
import java.util.Map;

/**
 * @author: lichengcan
 * @date: 2023-12-28 11:52
 * @description exchange
 **/
@RestController
@RequestMapping("/exchange")
public class ExchangeController {


    @Autowired
    RestTemplate restTemplate;


    @GetMapping("/getUserKeyValue")
    public User getUserKeyValue(Integer id, String name) {
        final String url = "http://localhost:8080/userKeyValue?id={id}&name={name}";
        return restTemplate.exchange(url, HttpMethod.GET, null, User.class, id, name).getBody();
    }
    

    @PostMapping("/getUserDomain")
    public User getUserDomain(@RequestBody(required = false) User user) {
        String url = "http://localhost:8080/userDomain";
        //请求头
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        headers.set("cc", "小灿12345");
        HttpEntity<User> request = new HttpEntity<>(user, headers);
        return restTemplate.exchange(url, HttpMethod.POST, request, User.class).getBody();
    }

    @PostMapping("/getUsersDomain")
    public Users getUsersDomain() {
        String url = "http://localhost:8080/usersDomain";
        //请求参数
        Users users = new Users();
        Map<String, Object> user = new HashMap<>(2);
        user.put("param1", "xxcan");
        user.put("param2", "xx12345");
        users.setId(12345L);
        users.setMap(user);
        //请求头
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        headers.set("cc", "小灿");
        HttpEntity<Users> request = new HttpEntity<>(users,headers);
        return restTemplate.exchange(url, HttpMethod.POST, request, Users.class).getBody();
    }

    @PostMapping("/getUserMap")
    public Map getUserMap() {
        String url = "http://localhost:8080/userMap";
        //请求参数
        Map<String, Object> users = new HashMap<>(2);
        Map<String,Object> user = new HashMap<>(2);
        user.put("name","灿灿");
        user.put("id",555L);
        users.put("param1", "xxcan");
        users.put("param2", "xx12345");
        users.put("user",user);
        //请求头
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        headers.set("cc", "小灿");
        HttpEntity<Map> request = new HttpEntity<>(users,headers);
        return restTemplate.exchange(url, HttpMethod.POST, request, Map.class).getBody();
    }
}

上面使用POST时会报错HttpClientErrorException 的 UnsupportedMediaType 错误。该错误表示请求的媒体类型不受支持。服务器返回了状态码 415（Unsupported Media Type）

解决在header中添加：

HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);

GetForObject方法

package com.cc.resttemplate.controller;

import com.cc.resttemplate.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.util.UriComponents;
import org.springframework.web.util.UriComponentsBuilder;

import javax.servlet.http.HttpServletRequest;
import java.net.URI;
import java.util.HashMap;
import java.util.Map;

/**
 * @author: lichengcan
 * @date: 2023-12-28 10:38
 * @description GetForObject
 **/

@RestController
@RequestMapping("/getForObject")
public class GetForObjectController {

    @Autowired
    RestTemplate restTemplate;

    /**
     * 1 传入一个值，返回一个对象的情况：
     * (列举了常用的，没有面面俱到，可以照猫画虎）
     * 1.1 直接将变量写在 url 中，记得添加注解 @PathVariable
     * 参数拼接在url上
     *
     * @param id
     * @return
     */
    @GetMapping("/findUserById/{id}")
    public User findUserById(@PathVariable Integer id) {
        String url = "http://localhost:8080/user/";
        return restTemplate.getForObject(url + id, User.class);
    }

    /**
     * 1.2 将变量通过key=word形式传递，
     * 通过 HttpServletRequest 获取参数
     * 地址栏 key=value 形式传参
     *
     * @param request
     * @return
     */
    @GetMapping("/findAUser")
    public User findAUser(HttpServletRequest request) {
        String id = request.getParameter("id");
        String url = "http://localhost:8080/userKeyValue?id=";
        return restTemplate.getForObject(url + id, User.class);
    }


    /**
     * 1.3 通过占位符：
     * 参数的不同传法 数字占位符
     *
     * @param id
     * @return
     */
    @GetMapping("/findOneUser/{id}")
    public User findOneUser(@PathVariable Integer id) {
        String url = "http://localhost:8080/user/{0}";
        return restTemplate.getForObject(url, User.class, id);
    }


    /**
     * 1.4 通过占位符，结合 Map：
     * 参数的不同传法，Map类型
     * 花括号里面的名字值和 map 的键名字保持一致即可，就可以传递对应的值。
     * @param id
     * @return
     */
    @GetMapping("/one/{id}")
    public User findOneUser(@PathVariable Long id) {
        Map<String, Long> map = new HashMap<String, Long>(2);
        map.put("id", id);
        return restTemplate.getForObject("http://localhost:8080/user/{id}", User.class, map);
    }


    /**
     * 1.5 通过 URI 进行 访问：
     * 使用 Spring 的 UriComponents 工具，参数可以整合到路径中。
     * @param request
     * @return
     */
    @GetMapping("/req")
    public User findAUser1(HttpServletRequest request) {
        Integer id = request.getParameter("id") == null ? 1 : Integer.valueOf(request.getParameter("id"));
        UriComponents uriComponents = UriComponentsBuilder.fromUriString("http://localhost:8080/userKeyValue?id=" + id).
                build().encode();
        URI uri = uriComponents.toUri();
        return restTemplate.getForObject(uri, User.class);
    }

    /**
     * 1.6 通过 append 拼接
     * @param id
     * @return
     */
    @GetMapping("/req1")
    public User findAUser2(Integer id) {
        UriComponents uriComponents = UriComponentsBuilder.fromUriString("http://localhost:8080/userKeyValue?id={id}").
                build().expand(id).encode();
        URI uri = uriComponents.toUri();
        return restTemplate.getForObject(uri, User.class);
    }


}

测试demo-被调用方

/*
 * Copyright 2013-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.cc.userdemo.controller;

import com.cc.userdemo.domain.User;
import com.cc.userdemo.domain.Users;
import org.springframework.web.bind.annotation.*;

import javax.servlet.http.HttpServletRequest;
import java.io.UnsupportedEncodingException;
import java.util.Map;

/**
 * @author lichengcan
 */
@RestController
@RequestMapping()
public class UserController {


    @GetMapping("/user/{id}")
    public User user(@PathVariable Long id) {
        User user = new User();
        user.setId(id);
        user.setName("cc");
        user.setAge(18);
        return user;
    }

    @GetMapping("/userKeyValue")
    public User userKeyValue(@RequestParam(required = false) Long id,
                             @RequestParam(required = false) String name) {
        User user = new User();
        user.setId(id == null ? 1 : id);
        user.setName(name == null ? "cc" : name);
        user.setAge(18);
        return user;
    }

    @PostMapping("/userDomain")
    public User userDomain(@RequestBody(required = false) User user, HttpServletRequest request) {
        user.setAge(188);
        //小灿乱码了
        try {
            System.out.println(new String(request.getHeader("cc").getBytes("ISO-8859-1"), "UTF-8"));
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }
        return user;
    }

    @PostMapping("/usersDomain")
    public Users usersDomain(@RequestBody(required = false) Users user, HttpServletRequest request) {
        try {
            System.out.println(new String(request.getHeader("cc").getBytes("ISO-8859-1"), "UTF-8"));
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }
        return user;
    }

    @PostMapping("/userMap")
    public Map userMap(@RequestBody(required = false) Map user, HttpServletRequest request) {
        try {
            System.out.println(new String(request.getHeader("cc").getBytes("ISO-8859-1"), "UTF-8"));
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }
        return user;
    }

}

User

@Data
public class User {
    private Long id;
    private String name;
    private Integer age;
}

Users

@Data
public class Users {
    private Long id;
    private String name;
    private Integer age;
    private Map map;
}