EmptyContentAsTreeTest.java

package com.fasterxml.jackson.databind.node;

import java.io.ByteArrayInputStream;
import java.io.StringReader;
import java.nio.charset.StandardCharsets;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.TreeNode;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;

import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.fail;

/**
 * Tests to verify handling of empty content with "readTree()"
 */
public class EmptyContentAsTreeTest extends DatabindTestUtil
{
    private final ObjectMapper MAPPER = objectMapper();

    private final String EMPTY0 = "";
    private final byte[] EMPTY0_BYTES = EMPTY0.getBytes(StandardCharsets.UTF_8);
    private final String EMPTY1 = "  \n\t  ";
    private final byte[] EMPTY1_BYTES = EMPTY1.getBytes(StandardCharsets.UTF_8);

    // [databind#1406]: when passing `JsonParser`, indicate lack of content
    // by returning `null`

    public void testNullFromEOFWithParserAndMapper() throws Exception
    {
        try (JsonParser p = MAPPER.createParser(EMPTY0)) {
            _assertNullTree(MAPPER.readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(EMPTY1)) {
            _assertNullTree(MAPPER.readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(new StringReader(EMPTY0))) {
            _assertNullTree(MAPPER.readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(new StringReader(EMPTY1))) {
            _assertNullTree(MAPPER.readTree(p));
        }

        try (JsonParser p = MAPPER.createParser(EMPTY0_BYTES)) {
            _assertNullTree(MAPPER.readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(EMPTY1_BYTES)) {
            _assertNullTree(MAPPER.readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(EMPTY1_BYTES, 0, EMPTY1_BYTES.length)) {
            _assertNullTree(MAPPER.readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(new ByteArrayInputStream(EMPTY0_BYTES))) {
            _assertNullTree(MAPPER.readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(new ByteArrayInputStream(EMPTY1_BYTES))) {
            _assertNullTree(MAPPER.readTree(p));
        }
    }

    // [databind#1406]
    public void testNullFromEOFWithParserAndReader() throws Exception
    {
        try (JsonParser p = MAPPER.createParser(EMPTY0)) {
            _assertNullTree(MAPPER.reader().readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(EMPTY1)) {
            _assertNullTree(MAPPER.reader().readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(new StringReader(EMPTY0))) {
            _assertNullTree(MAPPER.reader().readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(new StringReader(EMPTY1))) {
            _assertNullTree(MAPPER.reader().readTree(p));
        }

        try (JsonParser p = MAPPER.createParser(EMPTY0_BYTES)) {
            _assertNullTree(MAPPER.reader().readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(EMPTY1_BYTES)) {
            _assertNullTree(MAPPER.reader().readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(EMPTY1_BYTES, 0, EMPTY1_BYTES.length)) {
            _assertNullTree(MAPPER.reader().readTree(p));
        }

        try (JsonParser p = MAPPER.createParser(new ByteArrayInputStream(EMPTY0_BYTES))) {
            _assertNullTree(MAPPER.reader().readTree(p));
        }
        try (JsonParser p = MAPPER.createParser(new ByteArrayInputStream(EMPTY1_BYTES))) {
            _assertNullTree(MAPPER.reader().readTree(p));
        }
    }

    // [databind#2211]: when passing content sources OTHER than `JsonParser`,
    // return "missing node" instead of alternate (return `null`, throw exception).
    public void testMissingNodeForEOFOtherMapper() throws Exception
    {
        _assertMissing(MAPPER.readTree(EMPTY0));
        _assertMissing(MAPPER.readTree(EMPTY1));
        _assertMissing(MAPPER.readTree(new StringReader(EMPTY0)));
        _assertMissing(MAPPER.readTree(new StringReader(EMPTY1)));

        _assertMissing(MAPPER.readTree(EMPTY0_BYTES));
        _assertMissing(MAPPER.readTree(EMPTY0_BYTES, 0, EMPTY0_BYTES.length));
        _assertMissing(MAPPER.readTree(new ByteArrayInputStream(EMPTY0_BYTES)));
        _assertMissing(MAPPER.readTree(EMPTY1_BYTES));
        _assertMissing(MAPPER.readTree(EMPTY1_BYTES, 0, EMPTY1_BYTES.length));
        _assertMissing(MAPPER.readTree(new ByteArrayInputStream(EMPTY1_BYTES)));

        // Assume File, URL, etc are fine. Note: `DataInput` probably can't be made to
        // work since it can not easily/gracefully handle unexpected end-of-input
    }

    public void testMissingNodeViaObjectReader() throws Exception
    {
        _assertMissing(MAPPER.reader().readTree(EMPTY0));
        _assertMissing(MAPPER.reader().readTree(EMPTY1));
        _assertMissing(MAPPER.reader().readTree(new StringReader(EMPTY0)));
        _assertMissing(MAPPER.reader().readTree(new StringReader(EMPTY1)));

        _assertMissing(MAPPER.reader().readTree(EMPTY0_BYTES));
        _assertMissing(MAPPER.reader().readTree(EMPTY0_BYTES, 0, EMPTY0_BYTES.length));
        _assertMissing(MAPPER.reader().readTree(new ByteArrayInputStream(EMPTY0_BYTES)));
        _assertMissing(MAPPER.reader().readTree(EMPTY1_BYTES));
        _assertMissing(MAPPER.reader().readTree(EMPTY1_BYTES, 0, EMPTY1_BYTES.length));
        _assertMissing(MAPPER.reader().readTree(new ByteArrayInputStream(EMPTY1_BYTES)));
    }

    private void _assertNullTree(TreeNode n) {
        if (n != null) {
            fail("Should get `null` for reads with `JsonParser`, instead got: "+n.getClass().getName());
        }
    }

    private void _assertMissing(JsonNode n) {
        assertNotNull(n, "Should not get `null` but `MissingNode`");
        if (!n.isMissingNode()) {
            fail("Should get `MissingNode` but got: "+n.getClass().getName());
        }
    }
}