Question

我试图创建一个返回通用对象列表的方法，但我得到了ClassCastException。

HashMap<String, String> dados = new HashMap<>();
List<HashMap<String, String>> result = new ArrayList<>();

dados.put("sigla", "TST");
dados.put("nome", "Teste");
result.add(dados);

List<Posto> dadosProcessados = convertDados(Posto.class, result);

for (Posto posto : dadosProcessados) { //ClassCastException line 38
    System.out.println(posto.getSigla() + " => " + posto.getNome());
}

这是完整的方法：

public static <T> List<T> convertDados(Class<T> entity, List<HashMap<String, String>> dados) throws NoSuchMethodException, 
SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, InstantiationException {
    Field[] fields = entity.getDeclaredFields();
    Method[] allSetterMethods = entity.getMethods();
    Map<Integer, Method> setters = new HashMap<>();
    Class<?>[] paramTypes = new Class<?>[fields.length -1];
    List<T> result = new ArrayList<>();
    int cont  = 0;

    //Pega todos os setter
    for(Method method : allSetterMethods) {         
        if(method.getName().startsWith("set")) {
            paramTypes[cont] = method.getParameterTypes()[0];
            setters.put(cont, method);
            cont++;
        }
    }

    for (Field field : fields) {            
        for(Map.Entry<String, String> dado: dados.get(0).entrySet()) {
            if(dado.getValue() != null && field.getName().equals(dado.getKey())) {
                for(Map.Entry<Integer, Method> set : setters.entrySet()) {
                    if(set.getValue().getName().substring(3).equalsIgnoreCase(field.getName())) {
                        Method method = entity.getMethod(set.getValue().getName(), paramTypes[set.getKey()]);
                        method.invoke(entity.getConstructor().newInstance(), dado.getValue());
                        result.add((T) entity);
                        break;
                    }
                }
            }
        }
    }

错误堆栈跟踪

线程中的异常＆＃34; main＆＃34; java.lang.ClassCastException：java.lang.Class无法强制转换为beans.Teste.main中的data.bo.Posto（Teste.java:38）

Answer 1

您正在为结果添加result.add((T) entity);。实体是您传入的参数，它是一个类，而不是您想要的类型的实例。

也许您打算将entity.getConstructor().newInstance()的结果添加到列表中？

Answer 2

更改result.add（（T）实体）; with T obj = entity.getConstructor（）。newInstance（）;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Main {
  public static void main(String[] args) throws Exception {
    List<HashMap<String, String>> result = new ArrayList<>();

    HashMap<String, String> dados = new HashMap<>();

    dados.put("sigla", "TST");
    dados.put("nome", "Teste");
    result.add(dados);

    List<Posto> dadosProcessados = convertDados(Posto.class, result);

    for (Posto posto : dadosProcessados) {
      System.out.println(posto.getSigla() + " => " + posto.getNome());
    }

  }


  public static <T> List<T> convertDados(Class<T> entity, List<HashMap<String, String>> dados) throws NoSuchMethodException,
      SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, InstantiationException {
    Field[] fields = entity.getDeclaredFields();
    Method[] allSetterMethods = entity.getMethods();
    Map<Integer, Method> setters = new HashMap<>();
    Class<?>[] paramTypes = new Class<?>[fields.length];
    List<T> result = new ArrayList<>();
    int cont = 0;

    for (Method method : allSetterMethods) {
      if (method.getName().startsWith("set")) {
        paramTypes[cont] = method.getParameterTypes()[0];
        setters.put(cont, method);
        cont++;
      }
    }

    for (Field field : fields) {
      for (Map.Entry<String, String> dado : dados.get(0).entrySet()) {
        if (dado.getValue() != null && field.getName().equalsIgnoreCase(dado.getKey())) {
          for (Map.Entry<Integer, Method> set : setters.entrySet()) {
            if (set.getValue().getName().substring(3).equalsIgnoreCase(field.getName())) {
              Method method = entity.getMethod(set.getValue().getName(), paramTypes[set.getKey()]);
              T obj = entity.getConstructor().newInstance();
              method.invoke(obj, dado.getValue());
              result.add(obj);
              break;
            }
          }
        }
      }
    }

    return result;
  }
}

返回一个通用的List java

2 个答案: