我想在泛型类型上使用反射
我有这门课
package it.ciro.service;
import it.ciro.dao.SysMyAbDao;
import org.apache.log4j.Logger;
import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
/**
* Created by ciro on 09/12/2016.
*/
public class SelectOption<E extends Serializable> {
private SysMyAbDao dao;
private Class<E> entity;
private ArrayList<Class<E>> entityAll;
private Map<String,String> optionList = new HashMap<String,String>();
protected Logger logger;
public SelectOption(SysMyAbDao dao,Class<E> entity,String idName, String labelName ){
logger = Logger.getLogger(this.getClass());
this.dao = dao;
this.entity = entity;
entityAll = dao.findAll();
try{
Method idMethod = this.entity.getMethod(idName);
Method labelMethod = this.entity.getClass().getMethod(labelName);
for (Class<E> single : entityAll) {
optionList.put((String)idMethod.invoke(single),(String)labelMethod.invoke(single));
}
}catch (NoSuchMethodException ex){
ex.printStackTrace();
logger.error(ex.getMessage());
} catch (InvocationTargetException e) {
logger.error(e.getMessage());
} catch (IllegalAccessException e) {
logger.error(e.getMessage());
}
}
public Map<String, String> getOptionList() {
return optionList;
}
}
在我的 Controller 中
SelectOption<GeoProvince> selectOption = new SelectOption(geoRegionDao,GeoRegion.class,"idGeoRegion","name");
但我明白了
java.lang.NoSuchMethodException: java.lang.Class.idGeoRegion()
java 搜索泛型类型 e,而不是我在构造函数中使用的类型
我希望对我在 Controller 中使用的类型进行搜索。 GeoRegion 类中存在该方法。
这是 SysMyAbDao
public abstract class SysMyAbDao<T, E, Id extends Serializable> {
protected String message;
protected Boolean status;
protected T t ;
protected Logger logger;
protected Long totalRow;
private Class<T> type;
public SysMyAbDao(Class<T> type){
this.type = type;
}
.....
GeoRegion 类
public class GeoRegion implements java.io.Serializable {
private int idRegion;
private String name;
private String code;
private Set<GeoProvince> geoProvinces = new HashSet<GeoProvince>(0);
private Set<GeoCity> geoCities = new HashSet<GeoCity>(0);
public GeoRegion() {
}
public GeoRegion(int idRegion) {
this.idRegion = idRegion;
}
public GeoRegion(int idRegion, String name, String code, Set<GeoProvince> geoProvinces, Set<GeoCity> geoCities) {
this.idRegion = idRegion;
this.name = name;
this.code = code;
this.geoProvinces = geoProvinces;
this.geoCities = geoCities;
}
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="id_region", unique=true, nullable=false)
public int getIdRegion() {
return this.idRegion;
}
public void setIdRegion(int idRegion) {
this.idRegion = idRegion;
}
@Column(name="name")
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
@Column(name="code", unique=true)
public String getCode() {
return this.code;
}
public void setCode(String code) {
this.code = code;
}
@OneToMany(fetch=FetchType.LAZY, mappedBy="geoRegion")
public Set<GeoProvince> getGeoProvinces() {
return this.geoProvinces;
}
public void setGeoProvinces(Set<GeoProvince> geoProvinces) {
this.geoProvinces = geoProvinces;
}
@OneToMany(fetch=FetchType.LAZY, mappedBy="geoRegion")
public Set<GeoCity> getGeoCities() {
return this.geoCities;
}
public void setGeoCities(Set<GeoCity> geoCities) {
this.geoCities = geoCities;
}
}
最佳答案
您有一个额外的getClass()
在这一行中:
Method labelMethod = this.entity.getClass().getMethod(labelName);
事实上,您正在调用 getClass()
关于Class<E>
目的。并作为 Class<E>
的类(class)不是E
但是java.lang.Class
你得到NoSuchMethodException
你发布了。
您在其上调用方法的实例(在您的情况下是 single
)应该是 E
类型。且不是 Class<E>
类型.
总的来说,你最终会得到类似的结果:
public SelectOption(SysMyAbDao<E, ?, ? extends Serializable> dao,
Class<E> entityClass,
String idName,
String labelName) {
this.dao = dao;
this.entityClass = entityClass;
this.entityAll = dao.findAll(); // make sure your SysMyAbDao<E, ?, ?>#findAll() returns a Collection<E>
try{
Method idMethod = this.entityClass.getMethod(idName);
Method labelMethod = this.entityClass.getMethod(labelName);
for (E instance : entityAll) {
optionList.put((String)idMethod.invoke(instance),(String)labelMethod.invoke(instance));
}
} catch (NoSuchMethodException ex){
...
}
}
关于java getMethod() 泛型类型,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/41069450/