动态类型种姓弹簧路径变量

Question

我计划使用 JPA 创建一个简单的 Spring Rest Service 项目，该项目将根据路径变量中给出的实体名称和实体 ID 从数据库中获取详细信息。

请考虑以下代码。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import com.ds.dao.EntityDAO;
import com.ds.entities.Employees;
import javax.persistence.Entity;
@Controller
@RequestMapping("/")
public class DynaRestController {
@Autowired
EntityDAO entityDAO;

@RequestMapping(value = "{entityName}/{enityId}",method = RequestMethod.GET)
public @ResponseBody Object getEntity(@PathVariable("entityName") String entityName,@PathVariable("enityId") Object id) {
return entityDAO.getEntityById(entityName, id);
}
}

实体 DAO 类

public class EntityDAO {
@Autowired
EntityManager entityManager;

public Object getEntityById(String entityName, Object id) {
EntityType<?> entityType = getEntityByName(entityName);
Object idcasted = entityType.getIdType().getJavaType().cast(id);
System.out.println(idcasted.getClass().getName());
Object entity = entityManager.find(entityType.getJavaType(), idcasted);
System.out.println("Entity.. Name .." + entityName);
// Employees entity = session.load(Employees.class, id);
return entity;
}
private EntityType<?> getEntityByName(String name) {
Set<EntityType<?>> entities = entityManager.getMetamodel().getEntities();
for (Iterator<EntityType<?>> iterator = entities.iterator(); iterator.hasNext();) {
EntityType<?> entityType = (EntityType<?>) iterator.next();
if (entityType.getName().equals(name))
return entityType;
}
return null;
}

}

员工类

@Configurable
@Entity
@Table(name = "employees", catalog = "employees")
public class Employees implements java.io.Serializable {
/**
* 
*/
private static final long serialVersionUID = 1L;
private int empNo;
private Date birthDate;
private String firstName;
private String lastName;
private String gender;
private Date hireDate;
private Set<Titles> titleses = new HashSet<Titles>(0);
private Set<Salaries> salarieses = new HashSet<Salaries>(0);
private Set<DeptEmp> deptEmps = new HashSet<DeptEmp>(0);
private Set<DeptManager> deptManagers = new HashSet<DeptManager>(0);
public Employees() {
}
public Employees(int empNo, Date birthDate, String firstName, String lastName, String gender, Date hireDate) {
this.empNo = empNo;
this.birthDate = birthDate;
this.firstName = firstName;
this.lastName = lastName;
this.gender = gender;
this.hireDate = hireDate;
}
public Employees(int empNo, Date birthDate, String firstName, String lastName, String gender, Date hireDate,
Set<Titles> titleses, Set<Salaries> salarieses, Set<DeptEmp> deptEmps, Set<DeptManager> deptManagers) {
this.empNo = empNo;
this.birthDate = birthDate;
this.firstName = firstName;
this.lastName = lastName;
this.gender = gender;
this.hireDate = hireDate;
this.titleses = titleses;
this.salarieses = salarieses;
this.deptEmps = deptEmps;
this.deptManagers = deptManagers;
}
@Id
@Column(name = "emp_no", unique = true, nullable = false)
public int getEmpNo() {
return this.empNo;
}
public void setEmpNo(int empNo) {
this.empNo = empNo;
}
@Temporal(TemporalType.DATE)
@Column(name = "birth_date", nullable = false, length = 10)
public Date getBirthDate() {
return this.birthDate;
}
public void setBirthDate(Date birthDate) {
this.birthDate = birthDate;
}
@Column(name = "first_name", nullable = false, length = 14)
public String getFirstName() {
return this.firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
@Column(name = "last_name", nullable = false, length = 16)
public String getLastName() {
return this.lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
@Column(name = "gender", nullable = false, length = 2)
public String getGender() {
return this.gender;
}
public void setGender(String gender) {
this.gender = gender;
}
@Temporal(TemporalType.DATE)
@Column(name = "hire_date", nullable = false, length = 10)
public Date getHireDate() {
return this.hireDate;
}
public void setHireDate(Date hireDate) {
this.hireDate = hireDate;
}
@OneToMany(fetch = FetchType.LAZY, mappedBy = "employees")
public Set<Titles> getTitleses() {
return this.titleses;
}
public void setTitleses(Set<Titles> titleses) {
this.titleses = titleses;
}
@OneToMany(fetch = FetchType.LAZY, mappedBy = "employees")
public Set<Salaries> getSalarieses() {
return this.salarieses;
}
public void setSalarieses(Set<Salaries> salarieses) {
this.salarieses = salarieses;
}
@OneToMany(fetch = FetchType.LAZY, mappedBy = "employees")
@JsonBackReference
public Set<DeptEmp> getDeptEmps() {
return this.deptEmps;
}
public void setDeptEmps(Set<DeptEmp> deptEmps) {
this.deptEmps = deptEmps;
}
@OneToMany(fetch = FetchType.LAZY, mappedBy = "employees")
public Set<DeptManager> getDeptManagers() {
return this.deptManagers;
}
public void setDeptManagers(Set<DeptManager> deptManagers) {
this.deptManagers = deptManagers;
}

}

当我使用以下代码动态强制转换路径变量时

Object idcasted = entityType.getIdType().getJavaType().cast(id);
Object entity = entityManager.find(entityType.getJavaType(), idcasted);

它正在抛出 ClassCastExpcetion

java.lang.ClassCastException：无法将java.lang.String转换为int at java.lang.Class.cast(Class.java：3369( ~[na：1.8.0_112] at com.techm.att.ds.dao.EntityDAO.getEntityById(EntityDAO.java：33( ~[classes/：na] at com.techm.att.ds.dao.EntityDAO$$FastClassBySpringCGLIB$$8e64d745.invoke(( ~[classes/：na] at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java：204( ~[spring-core-4.3.13.RELEASE.jar：4.3.13.RELEASE] at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java：738( ~[spring-aop-4.3.13.RELEASE.jar：4.3.13.RELEASE] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java：157( ~[spring-aop-4.3.13.RELEASE.jar：4.3.13.RELEASE] at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java：136( ~[spring-tx-4.3.13.RELEASE.jar：4.3.13.RELEASE] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java：179( ~[spring-aop-4.3.13.RELEASE.jar：4.3.13.RELEASE]

任何帮助都将受到高度赞赏。

Answer 1

我给你写一个关于评论的简单例子。 这是相同的行为。你的 RestController 实际上得到一个字符串：

public static void main(String[] args) {
Object myString = "myString";
System.out.println(myString.getClass()); // class java.lang.String
int.class.cast(myString);
}

cast 方法检查给定值的实例，但失败：

public T cast(Object obj) {
if (obj != null && !isInstance(obj))
throw new ClassCastException(cannotCastMsg(obj));
return (T) obj;
}