Java have a native support for annotations.
I'm wondering if when I call obj.getAnnotation(Annotation.class), java stores class metadata in any kind of cache.
I have the same question with reflection like:
for (Method method : obj.getDeclaredMethods()) {
if (method.isAnnotationPresent(Annotation.class)) {
Annotation annotation = method.getAnnotation(Annotation.class);
Test test = (Test) annotation;
}
}
I have a two sets of Urls one for PreProd and one for Prod. Each Url has several API nodes. Instead of hard coding these API nodes, I maintain them in an enum
Something like this:
//PreProd
public enum PreProd
{
precheckorder,
submitresubmit,
creditInquiry,
createupdateorder,
confirmorder,
getorderstatus,
cancelorder,
}
/// <summary>
/// Gets the relative URL.
/// </summary>
/// <param name="u">The u.</param>
/// <returns></returns>
/// <exception cref="Exception"></exception>
public static string GetRelativeUrl(PreProd u)
{
switch (u)
{
case PreProd.precheckorder:
return "http://ift.tt/2mGaFQY";
case PreProd.submitresubmit:
return "http://ift.tt/2meUw7z";
case PreProd.creditInquiry:
return "http://ift.tt/2mGdr90";
case PreProd.createupdateorder:
return "http://ift.tt/2mf06Hc";
case PreProd.confirmorder:
return "http://ift.tt/2mG0LPj";
case PreProd.getorderstatus:
return "http://ift.tt/2mfc97e";
case PreProd.cancelorder:
return "http://ift.tt/2mGefKN";
default:
// Handle bad URL, possibly throw
throw new Exception();
}
}
//Prod
private enum Prod
{
precheckorder,
submitresubmit,
creditInquiry,
createupdateorder,
confirmorder,
getorderstatus,
cancelorder,
}
/// <summary>
/// Gets the relative URL.
/// </summary>
/// <param name="u">The u.</param>
/// <returns></returns>
/// <exception cref="Exception"></exception>
private static string GetRelativeUrl(Prod u)
{
switch (u)
{
case Prod.precheckorder:
return "http://ift.tt/2mf7xyh";
case Prod.submitresubmit:
return "http://ift.tt/2mG5Bfy";
case Prod.creditInquiry:
return "http://ift.tt/2mf9KtD";
case Prod.createupdateorder:
return "http://ift.tt/2mGachR";
case Prod.confirmorder:
return "http://ift.tt/2mf08Pk";
case Prod.getorderstatus:
return "http://ift.tt/2mG8IUu";
case Prod.cancelorder:
return "http://ift.tt/2mfdnzB";
default:
// Handle bad URL, possibly throw
throw new Exception();
}
}
We use environment variables to store the Environment name and thats what dictates which API set to use.
Ideally, I would like to have a single method, I pass in my environment and api name and it will return the API Url.
Something like
GettexApiUrlBasedOnEnvironment("Dev", "precheckorder");
and response will be
"http://ift.tt/2mGaFQY"
Any ideas/suggestions will be much appreciated. TIA
I try to get list of fields from class (hibernate entity). Like this:
Entity:
public class A {
public static final Integer someValue = 1;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "a_id")
private Integer id;
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "a_b_id", nullable = true)
private List<B> b;
@NotNull
@Column(name = "a_c_id")
private C c;
.........................
}
Method for getting non-static fields:
public static List<Field> getNonStaticFields(Class clazz) {
Field[] fields = clazz.getDeclaredFields();
List<Field> fieldsList = new ArrayList<>();
for (Field field : fields) {
if (!Modifier.isStatic(field.getModifiers())) {
fieldsList.add(field);
}
}
return fieldsList;
}
But I need to get only non-nullable non-static fields. This means that I need to get fields with @NotNull annotation and @JoinColumn annotation with parameter "nullable = false".
Check for @NotNull is simple:
field.isAnnotationPresent(NotNull.class)
But I have no idea how can I check field for @JoinColumn with parameter. How can I do it? Can somebody help me?
I have created three classes. Two classes Data and IntArrayEqualityComparer are below-
public class Data
{
public Dictionary<int[], List<double>> s = new Dictionary<int[], List<double>>(new IntArrayEqualityComparer());
public Data()
{
}
public Data(Dictionary<int[], List<double>> s)
{
this.s = s;
}
public Dictionary<int[], List<double>> S
{
get { return s; }
set { s = value; }
}
}
public class IntArrayEqualityComparer : IEqualityComparer<int[]>
{
public bool Equals(int[] x, int[] y)
{
if (x.Length != y.Length)
{
return false;
}
for (int i = 0; i < x.Length; i++)
{
if (x[i] != y[i])
{
return false;
}
}
return true;
}
public int GetHashCode(int[] obj)
{
int result = 17;
for (int i = 0; i < obj.Length; i++)
{
unchecked
{
result = result * 23 + obj[i];
}
}
return result;
}
}
A third class named Expression is created in which I need to convert LINQ expression into Reflection -
public class Expresion
{
public void CreateExpression()
{
Expression<Func<Data, List<int>>> exp1 = null;
//Below is the LINQ expression I want to convert
exp1 = p2 => p2.s[new int[] { 14, 5 }].Select((item, index) => new { item, index }).Select(x => x.index).ToList();
ParameterExpression p1 = Expression.Parameter(typeof(Data), "p");
MethodInfo mInfo = typeof(List<double>).GetMethod("get_Item");
MethodInfo mInfo1 = typeof(Dictionary<int, List<double>>).GetMethod("get_Item");
MethodInfo mInfo2 = typeof(Dictionary<int[], List<double>>).GetMethod("get_Item");
MethodInfo mInfo3 = typeof(List<int[]>).GetMethod("get_Item");
MemberExpression s1 = Expression.Property(p1, "s");
ParameterExpression index1 = Expression.Parameter(typeof(int), "index");
ParameterExpression item1 = Expression.Parameter(typeof(double), "item");
//Here I want to covert the "(item, index) => new { item, index }" part from LINQ expression into Reflection
}
}
I have some Action Attributes that allow parameters. This is how it looks like:
[DeleteActionCache(Action="GetTerms")]
public ActionResult AddTerm(string term){ }
public ActionResult GetTerms() {}
Now I want to get rid of the magic string "GetTerms" in my Attribute. So I would prefer something like: (Pseudocode, not working)
[DeleteActionCache(Action=this.GetTerms().GetType().Name)]
Having an additional Property inside my attribute-class and doing "Method2String"-Conversions inside my that class would be ok with me if this is needed to achieve what I want.
Info: I am not looking for a way the get the current method name (MethodBase.GetCurrentMethod)
I encountered this exception when I was trying to call reflections.getMethodUsage(Method), using reflections library 0.9.10. JDK version: 1.8.0_121 64bit
Please investigate the relevant stacktrace below. Note that custom package names and class names are substituted:
Caused by: org.reflections.ReflectionsException: Can't resolve member named someClass.access$1300(someClass, anotherClass) #103
at org.reflections.util.Utils.getMembersFromDescriptors(Utils.java:125)
at org.reflections.Reflections.getMethodUsage(Reflections.java:574)
at myCustomScanner.getCallers(myCustomScanner.java:145)
at myCustomScanner.getBeanByMember(myCustomScanner.java:192)
at myCustomScanner.getCallers(myCustomScanner.java:156)
at myCustomScanner.getBeanByMember(myCustomScanner.java:192)
at myCustomScanner.lambda$getServiceBeans$2(myCustomScanner.java:113)
at java.lang.Iterable.forEach(Iterable.java:75)
at myCustomScanner.getServiceBeans(myCustomScanner.java:111)
at myCustomScanner.scan(myCustomScanner.java:87)
at com.marvel.service.scanner.App.run(App.java:47)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:366)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeInitMethods(InitDestroyAnnotationBeanPostProcessor.java:311)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:134)
... 22 more
Caused by: org.reflections.ReflectionsException: Can't resolve member named 1300 for class someClass.access
at org.reflections.util.Utils.getMemberFromDescriptor(Utils.java:94)
at org.reflections.util.Utils.getMembersFromDescriptors(Utils.java:123)
... 39 more
Progress I made so far: This weird member name '1300' and class name suffix '.access' seem to come from an anonymous class' method. I also found that the MemberUsageScanner is using javassist library to obtain this kind of info under the hood, but I failed to debug the process when MemberUsageScanner is scanning the members by setting a conditional breakpoint in Eclipse, the process seem to never reach that breakpoint and never proceed, hanging in the middle of nowhere.
Hi I'm looking for a function like this:
var fieldName string = getFieldName((&myStruct{}).AField)
log.Println(fieldName)//==> "AField"