Spring TypeDescriptor test.

gistfile1.java

package com.github.ryoasai;

import static org.hamcrest.CoreMatchers.*;
import static org.junit.Assert.*;

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.hamcrest.Matcher;
import org.junit.Test;
import org.springframework.core.MethodParameter;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.util.ReflectionUtils;

public class TypeDescriptorTest {

    String[] strArray = { "test1", "test2" };
    List<String> strList = Arrays.asList("test", "test2");

    Map<String, Integer> map = new HashMap<String, Integer>();

    @SuppressWarnings("unchecked")
    List<List<String>> strListList = Arrays.asList(strList);

    List<String> sampleMethod(List<Integer> intList) {
        return null;
    }
    
    public static Matcher<Class<?>> isSameClassAs(Class<?> clazz) {
        @SuppressWarnings("unchecked") //double cast idiom
        Matcher<Class<?>> result = (Matcher<Class<?>>)(Matcher<?>)is((Object)clazz);
        
        return result;
    }

    // Resolve type from field declaration.

    @Test
    public void testResolveFieldType() {
        TypeDescriptor typeDesc = new TypeDescriptor(ReflectionUtils.findField(getClass(), "strList"));

        assertThat(typeDesc.getType(), isSameClassAs(List.class));
        assertThat(typeDesc.getElementType(), isSameClassAs(String.class));

        assertThat(typeDesc.asString(), is("java.util.List<java.lang.String>"));
        assertThat(typeDesc.isCollection(), is(true));
    }

    @Test
    public void testResolveFieldType_NestedType() {
        TypeDescriptor typeDesc = new TypeDescriptor(ReflectionUtils.findField(getClass(), "strListList"));

        assertThat(typeDesc.getType(), isSameClassAs(List.class));
        assertThat(typeDesc.getElementType(), isSameClassAs(List.class));

        assertThat(typeDesc.asString(), is("java.util.List<java.util.List<java.lang.String>>"));
        assertThat(typeDesc.isCollection(), is(true));

        TypeDescriptor elementTypeDesc = typeDesc.getElementTypeDescriptor();

        assertThat(elementTypeDesc.getType(), isSameClassAs(List.class));
        assertThat(elementTypeDesc.getElementType(), isSameClassAs(String.class));

        assertThat(elementTypeDesc.asString(), is("java.util.List<java.lang.String>"));
        assertThat(elementTypeDesc.isCollection(), is(true));
    }

    @Test
    public void testResolveFieldType_Map() {
        TypeDescriptor typeDesc = new TypeDescriptor(ReflectionUtils.findField(getClass(), "map"));

        assertThat(typeDesc.getType(), isSameClassAs(Map.class));
        assertThat(typeDesc.getMapKeyType(), isSameClassAs(String.class));
        assertThat(typeDesc.getMapValueType(), isSameClassAs(Integer.class));

        assertThat(typeDesc.asString(), is("java.util.Map<java.lang.String, java.lang.Integer>"));
        assertThat(typeDesc.isMap(), is(true));
    }
    
    // Resolve type from method declaration.

    @Test
    public void testResolveMethodParameterType() {
        Method sampleMethod = ReflectionUtils.findMethod(getClass(), "sampleMethod", List.class);

        TypeDescriptor typeDesc = new TypeDescriptor(new MethodParameter(sampleMethod, 0));

        assertThat(typeDesc.getType(), isSameClassAs(List.class));
        assertThat(typeDesc.getElementType(), isSameClassAs(Integer.class));
        
        assertThat(typeDesc.asString(), is("java.util.List<java.lang.Integer>"));
        assertThat(typeDesc.isCollection(), is(true));
    }

    @Test
    public void testResolveMethodReturnType() {
        Method sampleMethod = ReflectionUtils.findMethod(getClass(), "sampleMethod", List.class);

        TypeDescriptor typeDesc = new TypeDescriptor(new MethodParameter(sampleMethod, -1));

        assertThat(typeDesc.getType(), isSameClassAs(List.class));
        assertThat(typeDesc.getElementType(), isSameClassAs(String.class));

        assertThat(typeDesc.asString(), is("java.util.List<java.lang.String>"));
        assertThat(typeDesc.isCollection(), is(true));
    }

    static abstract class Parent<T> {
        abstract List<T> getList();
    }
    
    static class Child extends Parent<String> {
        @Override
        List<String> getList() {
            return new ArrayList<String>();
        }
    }

    // Resolve covariant return type
    @Test
    public void testResolveCovariantMethodReturnType() {
        Method methodWithCovariantReturnType = ReflectionUtils.findMethod(Child.class, "getList");
        
        TypeDescriptor typeDesc = new TypeDescriptor(new MethodParameter(methodWithCovariantReturnType, -1));
        
        assertThat(typeDesc.getType(), isSameClassAs(List.class));
        assertThat(typeDesc.getElementType(), isSameClassAs(String.class));
    }
    
    
    // Resolve type from instance.
    @Test
    public void testResolveArrayElementType() {
        TypeDescriptor typeDesc = TypeDescriptor.forObject(strArray);
        assertThat(typeDesc.getElementType(), isSameClassAs(String.class));

        assertThat(typeDesc.asString(), is("java.lang.String[]"));
        assertThat(typeDesc.isArray(), is(true));
    }

    @Test
    public void testResolveCollectionElementType() {
        TypeDescriptor typeDesc = TypeDescriptor.forObject(strList);
        assertThat(typeDesc.getElementType(), isSameClassAs(String.class));

        assertThat(typeDesc.asString(), is("java.util.Arrays$ArrayList<java.lang.String>"));
        assertThat(typeDesc.isCollection(), is(true));
    }
}