SpringBoot RestTemplate使用泛型

ps：推薦使用Feign

package com.example.demo;

import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.type.TypeFactory;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * SpringBoot restTemplate使用泛型，Result、Person、服務端代碼就不放出了
 */
@SpringBootTest
class BusinessApplicationTests {

    @Autowired
    public RestTemplate restTemplate;

    private static final ObjectMapper objectMapper = new ObjectMapper();

    @Test
    void test1() {
        // Result<List>
        String url = "http://127.0.0.1/1";
        JavaType javaType = objectMapper.getTypeFactory().constructParametricType(Result.class, List.class);
        ParameterizedTypeReference<Object> reference = ParameterizedTypeReference.forType(javaType);
        ResponseEntity<Object> entity = restTemplate.exchange(url, HttpMethod.POST, new HttpEntity<>(null), reference);
    }

    @Test
    void test2() {
        // Result<List<Person>>
        String url = "http://127.0.0.1/2";
        TypeFactory typeFactory = objectMapper.getTypeFactory();
        JavaType inner = typeFactory.constructParametricType(List.class, Person.class);
        JavaType javaType = typeFactory.constructParametricType(Result.class, inner);
        ParameterizedTypeReference<Object> reference = ParameterizedTypeReference.forType(javaType);
        ResponseEntity<Object> entity = restTemplate.exchange(url, HttpMethod.POST, new HttpEntity<>(null), reference);
    }

    @Test
    void test3() {
        // Result<Person>
        String url = "http://127.0.0.1/3";
        TypeFactory typeFactory = objectMapper.getTypeFactory();
        JavaType javaType = typeFactory.constructParametricType(Result.class, Person.class);
        ParameterizedTypeReference<Object> reference = ParameterizedTypeReference.forType(javaType);
        ResponseEntity<Object> entity = restTemplate.exchange(url, HttpMethod.POST, new HttpEntity<>(null), reference);
    }

    /**
     * 一個通用方法
     *
     * @param url
     * @param param
     * @param parameterClasses
     * @return
     */
    public ResponseEntity<Object> _doPost(String url, Map<String, String> param, Class<?>... parameterClasses) {
        TypeFactory typeFactory = objectMapper.getTypeFactory();
        ParameterizedTypeReference<Object> reference = null;
        JavaType javaType = null;
        int length = parameterClasses.length;
        if (length == 1) {
            javaType = typeFactory.constructParametricType(Result.class, parameterClasses);
        } else {
            javaType = typeFactory.constructParametricType(parameterClasses[length - 2], parameterClasses[length - 1]);
            for (int i = length - 3; i >= 0; i--) {
                javaType = typeFactory.constructParametricType(parameterClasses[i], javaType);
            }
            javaType = typeFactory.constructParametricType(Result.class, javaType);
        }
        reference = ParameterizedTypeReference.forType(javaType);
        return restTemplate.exchange(url, HttpMethod.POST, new HttpEntity<>(param), reference);
    }

    @Test
    void test4() {
        String url1 = "http://127.0.0.1/1";
        String url2 = "http://127.0.0.1/2";
        String url3 = "http://127.0.0.1/3";
        ResponseEntity<Object> entity1 = _doPost(url1, null, List.class);
        ResponseEntity<Object> entity2 = _doPost(url2, null, List.class, Person.class);
        ResponseEntity<Object> entity3 = _doPost(url3, null, Person.class);

    }
}