Given the java codes below:
public static Hashtable<String[],Integer> testTable = new Hashtable<String[],Integer>();
public static String [] compositeKey = {"key1","key2","key3"};
public static String [] testKey = {"key1","key2","key3"};
public static void main(String[] args) throws IOException{
if (!testTable.containsKey(compositeKey)){
testTable.put(compositeKey,1);
}
if(testTable.containsKey(testKey)){
System.out.println("got!");
}
System.out.println(testTable.get(testKey));
}
The output from console is:
null
It uses a String array as a key, and the 'testKey''s content is the same as 'compositeKey'. Why the output is null? Originally I am thinking the output should be:
got!
1
And what should I do if I want to use a composite key like this?
The problem is that String[] equals uses the default Object.equals implementation and only compares object identities.
What you'll need to do is make your String arrays into List objects that properly implement equals for an array of things.
Try this instead:
public class Test {
public static Hashtable<List<String>, Integer> testTable = new Hashtable<List<String>, Integer>();
public static String[] compositeKey = { "key1", "key2", "key3" };
public static String[] testKey = { "key1", "key2", "key3" };
public static List<String> compositeKeyList = Arrays.asList(compositeKey);
public static List<String> testKeyList = Arrays.asList(testKey);
public static void main(String[] args) {
if (!testTable.containsKey(compositeKeyList)) {
testTable.put(compositeKeyList, 1);
}
if (testTable.containsKey(testKeyList)) {
System.out.println("got!");
}
System.out.println(testTable.get(testKeyList));
}
}
Your two arrays are different objects, so they are not equal, even when their contents are equal.
Related
I am new to DynamoDB and wanted to know how can we query on a table in DynamoDB by using ONLY partition key in JAVA
I have table called "ervive-pdi-data-invalid-qa" and it's Schema is :
partition key is "SubmissionId"
Sort key is "Id".
City (Attribute)
Errors (Attribute)
The table looks like this:
Table
I want to retrieve the sort key value and remaining attributes data by using Partition key using (software.amazon.awssdk) new version of AWS SDK DynamoDB classes.
is it possible to get it? If so, can any one post the answers?
Have tried this:
DynamoDbClient ddb =
DynamoDbClient.builder().region(Region.US_EAST_1).build();
DynamoDbEnhancedClient enhancedClient =
DynamoDbEnhancedClient.builder()
.dynamoDbClient(ddb)
.build();
//Define table
DynamoDbTable<ErvivePdiDataInvalidQa> table =
enhancedClient.table("ervive-pdi-data-invalid-qa",
TableSchema.fromBean(ErvivePdiDataInvalidQa.class));
Key key = Key.builder().partitionValue(2023).build();
ErvivePdiDataInvalidQa result = table.getItem(r->r.key(key));
System.out.println("The record id is "+result.getId());
ErvivePdiDataInvalidQa table class is in below comment*
and it is returning "The provided key element does not match the schema (Service: DynamoDb, Status Code: 400, Request ID: PE1MKPMQ9MLT51OLJQVDCURQGBVV4KQNSO5AEMVJF66Q9ASUAAJG, Extended Request ID: null)"
Query you need is documented in one of the examples of AWS Dynamodb Query API for Java.
AmazonDynamoDB client = AmazonDynamoDBClientBuilder.standard()
.withRegion(Regions.US_WEST_2).build();
DynamoDB dynamoDB = new DynamoDB(client);
Table table = dynamoDB.getTable("ervive-pdi-data-invalid-qa");
QuerySpec spec = new QuerySpec()
.withKeyConditionExpression("SubmissionId = :v_id")
.withValueMap(new ValueMap()
.withInt(":v_id", 2146));
ItemCollection<QueryOutcome> items = table.query(spec);
Iterator<Item> iterator = items.iterator();
Item item = null;
while (iterator.hasNext()) {
item = iterator.next();
System.out.println(item.toJSONPretty());
}
A single Query operation can retrieve a maximum of 1 MB of data, see documentation
I have been working with Padma on this issue. We first tried A. Khan's code but could not get passed authentication with v1. Instead we got "WARNING: Your profile name includes a 'profile ' prefix. This is considered part of the profile name in the Java SDK, so you will need to include this prefix in your profile name when you reference this profile from your Java code."
ultimately it could not get the credentials. Our credentials assume IAM roles in .aws/config-i2 file. It works fine in v2 but not v1.
So then we tried v2 of the SDK and have no problems with connecting but we get NULL returned on trying to fetch all records from the table.
In all of the below attempts using v2 of SDK, table data returns NULL
We created this table class
package data;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbBean;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbPartitionKey;
import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbSortKey;
#DynamoDbBean
public class ErvivePdiDataInvalidQa {
private int submissionId;
private String id;
private String address1;
private String city;
private String dateOfBirth;
private String errors;
private String firstName;
private String firstNameNormalized;
private String gender;
private String lastName;
private String lastNameNormalized;
private String middleNameInitial;
private String postalCode;
private String rowNumber;
private String state;
private String submissionType;
#DynamoDbPartitionKey
public int getSubmissionId() {
return submissionId;
}
public void setSubmissionId(int submissionId) {
this.submissionId = submissionId;
}
#DynamoDbSortKey
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getAddress1() {
return address1;
}
public void setAddress1(String Address1) {
this.address1 = Address1;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getDateOfBirth() {
return dateOfBirth;
}
public void setDateOfBirth(String dateOfBirth) {
this.dateOfBirth = dateOfBirth;
}
public String getErrors() {
return errors;
}
public void setErrors(String errors) {
this.errors = errors;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getFirstNameNormalized() {
return firstNameNormalized;
}
public void setFirstNameNormalized(String firstNameNormalized) {
this.firstNameNormalized = firstNameNormalized;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getLastNameNormalized() {
return lastNameNormalized;
}
public void setLastNameNormalized(String lastNameNormalized) {
this.lastNameNormalized = lastNameNormalized;
}
public String getMiddleNameInitial() {
return middleNameInitial;
}
public void setMiddleNameInitial(String middleNameInitial) {
this.middleNameInitial = middleNameInitial;
}
public String getPostalCode() {
return postalCode;
}
public void setPostalCode(String postalCode) {
this.postalCode = postalCode;
}
public String getRowNumber() {
return rowNumber;
}
public void setRowNumber(String rowNumber) {
this.rowNumber = rowNumber;
}
public String getState() {
return state;
}
public void setState(String state) {
this.state = state;
}
public String getSubmissionType() {
return submissionType;
}
public void setSubmissionType(String submissionType) {
this.submissionType = submissionType;
}
}
DynamoDB code to get all records
//Connection
DynamoDbClient ddb = DynamoDbClient.builder().build();
DynamoDbEnhancedClient enhancedClient = DynamoDbEnhancedClient.builder()
.dynamoDbClient(ddb)
.build();
//Define table
DynamoDbTable<ErvivePdiDataInvalidQa> table = enhancedClient.table("ervive-pdi-data-invalid-qa", TableSchema.fromBean(ErvivePdiDataInvalidQa.class));
//Get All Items from table - RETURNING NULL
Iterator<ErvivePdiDataInvalidQa> results = table.scan().items().iterator();
while (results.hasNext()) {
ErvivePdiDataInvalidQa rec = results.next();
System.out.println("The record id is "+rec.getId());
}
Also tried:
DynamoDB code to filter by SubmissionID
AttributeValue attr = AttributeValue.builder()
.n("1175")
.build();
// Get only Open items in the Work table
Map<String, AttributeValue> myMap = new HashMap<>();
myMap.put(":val1", attr);
Map<String, String> myExMap = new HashMap<>();
myExMap.put("#sid", "SubmissionId");
// Set the Expression so only Closed items are queried from the Work table
Expression expression = Expression.builder()
.expressionValues(myMap)
.expressionNames(myExMap)
.expression("#sid = :val1")
.build();
ScanEnhancedRequest enhancedRequest = ScanEnhancedRequest.builder()
.filterExpression(expression)
.limit(15)
.build();
// Get items in the Record table and write out the ID value
Iterator<ErvivePdiDataInvalidQa> results = table.scan(enhancedRequest).items().iterator();
while (results.hasNext()) {
ErvivePdiDataInvalidQa record = results.next();
System.out.println("The record id is " + record.getId());
}
I was using org.apache.commons.collections.CollectionUtils and for this version using find method was like this:
BeanPropertyValueEqualsPredicate objIdEqualsPredicate = new BeanPropertyValueEqualsPredicate("objId", objId);
myObj = (MyClass) CollectionUtils.find(myObjSet, objIdEqualsPredicate);
But with org.apache.commons.collections4.CollectionUtils, I don't know how to make it work.
Here what I do now but if there is a clear way of it, I will be glad to learn:
Predicate<MyClass> objIdEqualsPredicate = new Predicate<MyClass>() {
#Override
public boolean evaluate(MyClass obj) {
return obj.getObjId().equals(objId);
}
};
myObj = CollectionUtils.find(myObjSet, objIdEqualsPredicate);
Is there a way to filter some objects according to the their fields' values. If possible I don't want to use anonymous class for this.
Thanks.
As the common-beanutils still have commons-collections as dependency, you must implement the Predicate interface.
For example you can take the source code of BeanPropertyValueEqualsPredicate and refactor it, so your version implements the org.apache.commons.collections4.Predicate interface.
Or you write your own version. I would prefer not to use anonymous inner classes, because of the possibility to write unit tests for the predicate and reuse it.
Quick Example (not nullsafe,..)
#Test
public class CollectionsTest {
#Test
void test() {
Collection<Bean> col = new ArrayList<>();
col.add(new Bean("Foo"));
col.add(new Bean("Bar"));
Predicate<Bean> p = new FooPredicate("Bar");
Bean find = CollectionUtils.find(col, p);
Assert.assertNotNull(find);
Assert.assertEquals(find.getFoo(), "Bar");
}
private static final class FooPredicate implements Predicate<CollectionsTest.Bean> {
private String fieldValue;
public FooPredicate(final String fieldValue) {
super();
this.fieldValue = fieldValue;
}
#Override
public boolean evaluate(final Bean object) {
// return true for a match - false otherwise
return object.getFoo().equals(fieldValue);
}
}
public static class Bean {
private final String foo;
Bean(final String foo) {
super();
this.foo = foo;
}
public String getFoo() {
return foo;
}
}
}
I'm using Reflection to work out my project classes with the Generics from a third party, however, I keep getting the error "Late bound operations cannot be performed on types or methods for which ContainsGenericParameters is true." when I try to Invoke an static method from an static generic class which contains generics invocation.
Third Party code looks like this
public interface INestedGeneric<TResult>
{
INestedGeneric<TResult> DoSomethingElse();
}
public static class GenericClass<TResult> where TResult : new()
{
public static INestedGeneric<TResult> DoSomething()
{ return new NestedClass<TResult>(); }
}
public class NestedClass<TResult> : INestedGeneric<TResult>
{
public INestedGeneric<TResult> DoSomethingElse()
{ return new NestedClass<TResult>(); }
}
My code looks like:
public class Someone
{
private int _integerProperty;
private string _stringProperty;
public int IntegerProperty
{
get { return _integerProperty; }
set { _integerProperty = value; }
}
public string StringProperty
{
get { return _stringProperty; }
set { _stringProperty = value; }
}
}
static void Main(string[] args)
{
Type classType = typeof(Someone);
Type theclass = typeof(GenericClass<>); theclass.MakeGenericType(classType);
Type theinterface = typeof(INestedGeneric<>); theinterface.MakeGenericType(classType);
MethodInfo dosomething = theclass.GetMethod("DoSomething", BindingFlags.Public | BindingFlags.Static);
dosomething.Invoke(null, null);
dosomething = null;
}
Any idea how to invoke the method strictly in this scenario? I have read and try the help from other posts, but didn't work.
Thank you so much...
I already figure it out. The solution was to use the type provided by the MakeGenericType method.
Like this:
...
Type theclass = typeof(GenericClass<>).MakeGenericType(classType);
Type theinterface = typeof(INestedGeneric<>).MakeGenericType(classType);
MethodInfo dosomething = theclass.GetMethod("DoSomething", BindingFlags.Public | BindingFlags.Static);
dosomething.Invoke(null, null);
...
I would like to write something like :
#Autowired
private SpringTemplateEngine engine;
....
// Thymeleaf Context
WebContext thymeleafContext = new WebContext(request, response, request.getServletContext(), locale);
// cached html of a thymeleaf template file
String cachedHtml=....
// process the cached html
String html=engine.process(cachedHtml, thymeleafContext);
By default, the [process] method can't do that. I can understand from the docs that I need a special Template Resolver :
In order to execute templates, the process(String, IContext) method will be used:
final String result = templateEngine.process("mytemplate", ctx);
The "mytemplate" String argument is the template name, and it will relate to the physical/logical location of the template itself in a way configured at the template resolver/s.
Does anyone know how to solve my problem ?
The goal is to cache the Thymeleaf templates (files) in strings and then process theses strings rather than the files.
The solution we ended up using consisted of a new IResourceResolver with a custom Context rather than a custom TemplateResolver. We chose this because we still wanted to use classpath scanning in most cases, but occasionally had dynamic content.
The following shows how we did it:
public class StringAndClassLoaderResourceResolver implements IResourceResolver {
public StringAndClassLoaderResourceResolver() {
super();
}
public String getName() {
return getClass().getName().toUpperCase();
}
public InputStream getResourceAsStream(final TemplateProcessingParameters params, final String resourceName) {
Validate.notNull(resourceName, "Resource name cannot be null");
if( StringContext.class.isAssignableFrom( params.getContext().getClass() ) ){
String content = ((StringContext)params.getContext()).getContent();
return IOUtils.toInputStream(content);
}
return ClassLoaderUtils.getClassLoader(ClassLoaderResourceResolver.class).getResourceAsStream(resourceName);
}
public static class StringContext extends Context{
private final String content;
public StringContext(String content) {
this.content = content;
}
public StringContext(String content, Locale locale) {
super(locale);
this.content = content;
}
public StringContext(String content, Locale locale, Map<String, ?> variables) {
super(locale, variables);
this.content = content;
}
public String getContent() {
return content;
}
}
Test Case
public class StringAndClassLoaderResourceResolverTest {
private static SpringTemplateEngine templateEngine;
#BeforeClass
public static void setup(){
TemplateResolver resolver = new TemplateResolver();
resolver.setResourceResolver(new StringAndClassLoaderResourceResolver());
resolver.setPrefix("mail/"); // src/test/resources/mail
resolver.setSuffix(".html");
resolver.setTemplateMode("LEGACYHTML5");
resolver.setCharacterEncoding(CharEncoding.UTF_8);
resolver.setOrder(1);
templateEngine = new SpringTemplateEngine();
templateEngine.setTemplateResolver(resolver);
}
#Test
public void testStringResolution() {
String expected = "<div>dave</div>";
String input = "<div th:text=\"${userName}\">Some Username Here!</div>";
IContext context = new StringAndClassLoaderResourceResolver.StringContext(input);
context.getVariables().put("userName", "dave");
String actual = templateEngine.process("redundant", context);
assertEquals(expected, actual);
}
#Test
public void testClasspathResolution(){
IContext context = new Context();
context.getVariables().put("message", "Hello Thymeleaf!");
String actual = templateEngine.process("dummy", context);
String expected = "<h1>Hello Thymeleaf!</h1>";
assertEquals(expected, actual);
}
}
Dummy template file at src/main/resources/mail/dummy.html
<h1 th:text="${message}">A message will go here!</h1>
Note: We used Apache CommonsIO's IOUtils for converting the String to an InputStream
You can implement your own TemplateResolver and IResourceResolver to work with String.
for simple unit tests:
static class TestResourceResolver implements IResourceResolver {
public String content = "";
#Override
public String getName() {
return "TestTemplateResolver";
}
#Override
public InputStream getResourceAsStream(TemplateProcessingParameters templateProcessingParameters,
String resourceName) {
return new ByteArrayInputStream(content.getBytes());
}
}
or just use org.thymeleaf.templateresolver.StringTemplateResolver in Thymeleaf 3
Yep StringTemplateResolver is the way to go.
public class ReportTemplateEngine {
private static TemplateEngine instance;
private ReportTemplateEngine() {}
public static TemplateEngine getInstance() {
if(instance == null){
synchronized (ReportTemplateEngine.class) {
if(instance == null) {
instance = new TemplateEngine();
StringTemplateResolver templateResolver = new StringTemplateResolver();
templateResolver.setTemplateMode(TemplateMode.HTML);
instance.setTemplateResolver(templateResolver);
}
}
}
return instance;
}
}
I have a Sharp Architecture based app using Fluent NHibernate with Automapping. I have the following Enum:
public enum Topics
{
AdditionSubtraction = 1,
MultiplicationDivision = 2,
DecimalsFractions = 3
}
and the following Class:
public class Strategy : BaseEntity
{
public virtual string Name { get; set; }
public virtual Topics Topic { get; set; }
public virtual IList Items { get; set; }
}
If I create an instance of the class thusly:
Strategy s = new Strategy { Name = "Test", Topic = Topics.AdditionSubtraction };
it Saves correctly (thanks to this mapping convention:
public class EnumConvention : IPropertyConvention, IPropertyConventionAcceptance
{
public void Apply(FluentNHibernate.Conventions.Instances.IPropertyInstance instance)
{
instance.CustomType(instance.Property.PropertyType);
}
public void Accept(FluentNHibernate.Conventions.AcceptanceCriteria.IAcceptanceCriteria criteria)
{
criteria.Expect(x => x.Property.PropertyType.IsEnum);
}
}
However, upon retrieval (when SQLite is my db) I get an error regarding an attempt to convert Int64 to Topics.
This works fine in SQL Server.
Any ideas for a workaround?
Thanks.
Actually, it is possible to map enums to INT, but in SQLite, INT will come back as an Int64, and, since you can't specify that your enum is castable to long, you will get this error. I am using NHibernate, so my workaround was to create a custom AliasToBean class that handles converting the enum fields to Int32:
public class AliasToBeanWithEnums<T> : IResultTransformer where T : new()
{
#region IResultTransformer Members
public IList TransformList(IList collection)
{
return collection;
}
public object TransformTuple(object[] tuple, string[] aliases)
{
var t = new T();
Type type = typeof (T);
for (int i = 0; i < aliases.Length; i++)
{
string alias = aliases[i];
PropertyInfo prop = type.GetProperty(alias);
if (prop.PropertyType.IsEnum && tuple[i] is Int64)
{
prop.SetValue(t, Convert.ToInt32(tuple[i]), null);
continue;
}
prop.SetValue(t, tuple[i], null);
}
return t;
}
#endregion
}
Usage:
public IList<ItemDto> GetItemSummaries()
{
ISession session = NHibernateSession.Current;
IQuery query = session.GetNamedQuery("GetItemSummaries")
.SetResultTransformer(new AliasToBeanWithEnums<ItemDto>());
return query.List<ItemDto>();
}
By default, emums are automapped to strings for SQLite (don't know what happens with SQL Server).
Less efficient storage wise, obviously, but that might be a non-issue unless you have really huge data sets.