使用RestTemplate获取XML对象列表为空问题的解决方案

<ArrayOfObject>
    <Object>
        <id>1</id>
        <name>Item A</name>
        <var1>Value1A</var1>
        <var2>Value2A</var2>
        <var3>Value3A</var3>
    </Object>
    <Object>
       <id>2</id>
       <name>Item B</name>
       <var1>Value1B</var1>
       <var2>Value2B</var2>
       <var3>Value3B</var3>
   </Object>
   <!-- ... 更多Object元素 ... -->
</ArrayOfObject>

<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-xml</artifactId>
</dependency>
<dependency>
    <groupId>javax.xml.bind</groupId>
    <artifactId>jaxb-api</artifactId>
    <version>2.3.1</version> <!-- 根据Java版本选择合适的版本，Java 11+可能需要 -->
</dependency>

package it.me.model;

import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlRootElement;
import java.io.Serializable;

@JacksonXmlRootElement(localName = "Object") // 明确指定XML根元素名为"Object"
public class Object implements Serializable {

    private static final long serialVersionUID = 1L;

    @JacksonXmlProperty // 默认映射到同名字段
    private String id;

    @JacksonXmlProperty
    private String name;

    @JacksonXmlProperty
    private String var1;

    @JacksonXmlProperty
    private String var2;

    @JacksonXmlProperty
    private String var3;

    // 无参构造函数是Jackson反序列化的必要条件
    public Object() {}

    // 全参构造函数（可选，但推荐）
    public Object(String id, String name, String var1, String var2, String var3) {
        this.id = id;
        this.name = name;
        this.var1 = var1;
        this.var2 = var2;
        this.var3 = var3;
    }

    // Getters and Setters (Jackson需要它们来访问和设置字段值)
    public String getId() { return id; }
    public void setId(String id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public String getVar1() { return var1; }
    public void setVar1(String var1) { this.var1 = var1; }
    public String getVar2() { return var2; }
    public void setVar2(String var2) { this.var2 = var2; }
    public String getVar3() { return var3; }
    public void setVar3(String var3) { this.var3 = var3; }

    // toString, equals, hashCode 等方法（推荐重写，便于调试和使用）
    @Override
    public String toString() {
        return "Object{" +
               "id='" + id + '\'' +
               ", name='" + name + '\'' +
               ", var1='" + var1 + '\'' +
               ", var2='" + var2 + '\'' +
               ", var3='" + var3 + '\'' +
               '}';
    }
}

package it.me.model;

import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlElementWrapper;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlRootElement;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

@JacksonXmlRootElement(localName = "ArrayOfObject") // 明确指定XML根元素名为"ArrayOfObject"
public class ArrayOfObject implements Serializable {

    private static final long serialVersionUID = 1L;

    // 关键注解：
    // @JacksonXmlProperty(localName = "Object")：指定列表中的每个元素对应的XML标签名是"Object"
    // @JacksonXmlElementWrapper(useWrapping = false)：告诉Jackson，XML中没有额外的列表包装标签，
    //                                                <Object>元素直接作为<ArrayOfObject>的子元素。
    @JacksonXmlProperty(localName = "Object")
    @JacksonXmlElementWrapper(useWrapping = false)
    private List<Object> objects = new ArrayList<>(); // 字段名可以自由命名，但要通过注解正确映射

    public ArrayOfObject() {}

    public ArrayOfObject(List<Object> objects) {
        this.objects = objects;
    }

    // Getters and Setters
    public List<Object> getObjects() { return objects; }
    public void setObjects(List<Object> objects) { this.objects = objects; }

    @Override
    public String toString() {
        return "ArrayOfObject{" +
               "objects=" + objects +
               '}';
    }
}

package it.me.controller;

import it.me.model.ArrayOfObject;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import java.util.List;

@RestController
@RequestMapping("/api") // 建议为Controller添加一个基础路径
public class RestCallController {

    private final String EXTERNAL_API_URI = "http://localhost:8080/external/objects"; // 替换为实际的外部API地址

    @GetMapping("/objects")
    public List<Object> getObjectsFromExternalApi() {
        RestTemplate restTemplate = new RestTemplate();
        // 直接将XML反序列化为ArrayOfObject类型
        ArrayOfObject resultWrapper = restTemplate.getForObject(EXTERNAL_API_URI, ArrayOfObject.class);

        // 返回包装类中的列表
        return resultWrapper != null ? resultWrapper.getObjects() : new ArrayList<>();
    }
}