java.lang.ClassCastException: java.lang.String cannot be cast to [Ljava.lang.Object; - fetching a query from the database using hibernate [duplicate]

Question

I am trying to fetch a distinct record from the database. this is my attempt

@SuppressWarnings("unchecked")
    @Override
    public List<Employee> getAllEmployees(String employeeName) { 
    String query = "SELECT DISTINCT e.name FROM Employees e WHERE e.name like '%"+ employeeName +"%'";
        List<Object[]> employeeObjects = hibernateUtil.fetchAll(query);
        List<Employee> employees = new ArrayList<Employee>();
        for(Object[] employeeObject: employeeObjects) {
            Employee employee = new Employee();
            long id = ((BigInteger) employeeObject[0]).longValue();         
            int age = (int) employeeObject[1];
            String name = (String) employeeObject[2];
            float salary = (float) employeeObject[3];
            employee.setId(id);
            employee.setName(name);
            employee.setAge(age);
            employee.setSalary(salary);
            employees.add(employee);
        }
        System.out.println(employees);
        return employees;
    }

this is the line the error occurs

for(Object[] employeeObject: employeeObjects) { //line 65

When i try to search for the record I get this error

java.lang.ClassCastException: java.lang.String cannot be cast to [Ljava.lang.Object;
    com.ranga.dao.impl.EmployeeDAOImpl.getAllEmployees(EmployeeDAOImpl.java:65)
    com.ranga.service.impl.EmployeeServiceImpl.getAllEmployees(EmployeeServiceImpl.java:48)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:497)
    org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
    org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
    org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
    org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
    com.sun.proxy.$Proxy23.getAllEmployees(Unknown Source)
    com.ranga.controller.EmployeeController.searchEmployee(EmployeeController.java:73)

please what could be wrong?

No idea what hibernateUtil.fetchAll does - your problem is likely there. — Boris the Spider
– Boris the Spider, Commented Jul 7, 2016 at 11:11
@BoristheSpider: yes, but it's a cast to Ljava.lang.Object that causes the issue, not a cast to String — Stultuske
– Stultuske, Commented Jul 7, 2016 at 11:13
@Blaze that should not be a comment but in the question. It is extremely important to highlight the specific line the exception comes from when you post questions. — Boris the Spider
– Boris the Spider, Commented Jul 7, 2016 at 11:20

Boris the Spider · Accepted Answer · 2016-07-07 11:18:05Z

5

Your query is:

SELECT DISTINCT e.name FROM Employees e WHERE e.name like '%"+ employeeName +"%'

_{(Which is not parameterised. Bad. Very Bad. Naughty developer!)}

Therefore you select unique e.name from Employees - this means you get back some names.

Therefore I would suspect hibernateUtil.fetchAll returns a List<String>.

You do:

List<Object[]> employeeObjects = hibernateUtil.fetchAll(query);

Which I suspect is an unsafe cast from List<?> or List (raw).

You then do

for(Object[] employeeObject: employeeObjects) {
...
}

At this point Java will cast the item in the List to the required type, i.e. Object[]. Hence your error.

answered Jul 7, 2016 at 11:18

Boris the Spider

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