I am attempting to use OKHttp, Spring, and Jackson to retrieve JSON data from an API. At is most basic, the response from the API looks like:
{
"_page": 1,
"_total_items": 1,
"_items_this_page": 1,
"_index_start": 1,
"_index_end": 1,
"_links": {
"self": {
"href": ""
}
},
"some_key": [
{
"key": "value1"
},
{
"key": "value2"
}
]
}
I created a generic wrapper class:
public class PageWrapper<T> {
@JsonProperty("_links")
private PageLink links;
@JsonAlias({"documents", "employees"} )
private T pgData;
public T getPgData() {
return pgData;
}
public void setPgData(T pgData) {
this.pgData = pgData;
}
public PageLink getLinks() {
return links;
}
public void setLinks(PageLink links) {
this.links = links;
}
}
I created some tests to ensure it was being parsed correctly, and it worked as expected:
public void testEmployees() throws JsonParseException, JsonMappingException, IOException {
File file = new File(this.getClass().getClassLoader().getResource("employee.json").getFile());
var res = this.mapper.readValue(file, new TypeReference<PageWrapper<List<WBEmployee>>>() {
});
assertThat(res).isNotNull();
assertThat(res.getPgData().size()).isGreaterThan(0);
for(var r : res.getPgData()) {
assertThat(r.getAddress()).isNotNull();
assertThat(r.getBirthDate()).isNotBlank();
assertThat(r.getEmail()).isNotNull();
assertThat(r.getFirstName()).isNotNull();
assertThat(r.getLastName()).isNotNull();
}
}
The issue does not come until I run another test which interacts with the actual API:
@Test
public void testTestList() throws IOException {
var res = empAPI.getList();
assertThat(res).isNotNull();
assertThat(res.size()).isGreaterThan(0);
for(var r : res) {
assertThat(r.getAddress()).isNotNull();
assertThat(r.getBirthDate()).isNotBlank();
assertThat(r.getEmail()).isNotNull();
assertThat(r.getFirstName()).isNotNull();
assertThat(r.getLastName()).isNotNull();
}
}
This test calls the following method (through empAPI.getList()):
@Override
public <T> PageWrapper<List<T>> doNestedListGet(Class<T> type, HttpUrl url) throws IOException {
var req = this.reqBuilder.url(url).build();
try (var res = this.webClient.newCall(req).execute()) {
if (!res.isSuccessful()) {
throw new IOException(String.format("API call failed: %s", res));
}
var jString = res.body().string();
return this.mapper.readValue(jString, new TypeReference<PageWrapper<List<T>>>() {
});
}
}
In this example, jString and the contents of the file in the passing tests are the same (looked at them using the Debugger). However, I am receiving a class cast error:
java.lang.ClassCastException: class java.util.LinkedHashMap cannot be cast to class myClass
The getList() method called in the failing test looks like this:
public List<WBEmployee> getList(int page, WBEmploymentStatus employmentStatus) throws IOException {
var url = this.baseEndpoint.newBuilder()
.addQueryParameter("page", String.valueOf(page))
.addQueryParameter("status", employmentStatus.getDescr()).build();
return this.wbClient.doNestedListGet(WBEmployee.class, url).getPgData();
}
I am assuming the issue has to with the handling of generics (explicitly passing a class to TypeReference instead of T gets the expected results) , but not quite sure where the issue lies. Any advice would be appreciated.
Added full stack trace:
java.lang.ClassCastException: class java.util.LinkedHashMap cannot be cast to class com.midamcorp.wblib.model.WBEmployee (java.util.LinkedHashMap is in module java.base of loader 'bootstrap'; com.midamcorp.wblib.model.WBEmployee is in unnamed module of loader 'app')
at com.midamcorp.hcmadapter.client.EmployeeAPITest.testTestList(EmployeeAPITest.java:47)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:210)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:206)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:131)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:84)
at org.eclipse.jdt.internal.junit5.runner.JUnit5TestReference.run(JUnit5TestReference.java:98)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:40)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:768)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:464)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:210)
>>` to the TypeReference would have been the same as passing `PageWrapper
>>`. What am I missing.