Jackson-based body filter for JSON

logbook-json/src/main/java/org/zalando/logbook/json/JacksonJsonFieldBodyFilter.java

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+package org.zalando.logbook.json;
+
+import java.io.StringWriter;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+import org.zalando.logbook.BodyFilter;
+
+import com.fasterxml.jackson.core.JsonFactory;
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.JsonToken;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * 
+ * Thread-safe filter for JSON fields. Filters on property names.
+ * <br><br> 
+ * Output is always compacted, even in case of invalid JSON, 
+ * so this filter should not be used in conjunction with {@linkplain JsonCompactor}.
+ *
+ */
+
+@Slf4j
+public class JacksonJsonFieldBodyFilter implements BodyFilter {
+
+    private final static StringReplaceJsonCompactor fallbackCompactor = new StringReplaceJsonCompactor();
+
+    private final String replacement;
+    private final Set<String> fields;
+    private final ObjectMapper objectMapper;
+
+    public JacksonJsonFieldBodyFilter(Collection<String> fieldNames, String replacement, ObjectMapper objectMapper) {
+        this.fields = new HashSet<>(fieldNames); // thread safe for reading
+        this.replacement = replacement;
+        this.objectMapper = objectMapper;
+    }
+
+    public JacksonJsonFieldBodyFilter(Collection<String> fieldNames, String replacement) {
+        this(fieldNames, replacement, new ObjectMapper());
+    }
+
+    @Override
+    public String filter(String contentType, String body) {
+        return JsonMediaType.JSON.test(contentType) ? filter(body) : body;
+    }
+
+    public String filter(final String body) {
+        try {
+            JsonFactory factory = objectMapper.getFactory();
+            final JsonParser parser = factory.createParser(body);
+
+            StringWriter writer = new StringWriter(body.length() * 2); // rough estimate of final size
+
+            JsonGenerator generator = factory.createGenerator(writer);            
+            try {
+                while(true) {
+                    JsonToken nextToken = parser.nextToken();
+                    if(nextToken == null) {
+                        break;
+                    }
+
+                    generator.copyCurrentEvent(parser);
+                    if(nextToken == JsonToken.FIELD_NAME && fields.contains(parser.getCurrentName())) {
+                        nextToken = parser.nextToken();
+                        generator.writeString(replacement);
+                        if(!nextToken.isScalarValue()) {
+                            parser.skipChildren(); // skip children
+                        }
+                    }
+                }                    
+            } finally {
+                parser.close();
+
+                generator.close();
+            }
+
+            return writer.toString();
+        } catch(Exception e) {
+            log.trace("Unable to filter body for fields {}, compacting result. `{}`", fields, e.getMessage()); 
+            return fallbackCompactor.compact(body);
+        }
+    }
+
+}

logbook-json/src/test/java/org/zalando/logbook/json/JacksonJsonFieldBodyFilterTest.java

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+package org.zalando.logbook.json;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+
+import static org.hamcrest.MatcherAssert.*;
+import static org.hamcrest.Matchers.*;
+
+import org.junit.jupiter.api.Test;
+
+
+public class JacksonJsonFieldBodyFilterTest {
+
+    @Test
+    public void testFilterString() throws Exception {
+        String filtered = getFilter("email") .filter(getResource("/user.json"));
+        assertThat(filtered, not(containsString("@entur.org")));
+    }
+
+    @Test
+    public void testFilterNumber() throws Exception {
+        String filtered = getFilter("id") .filter(getResource("/user.json"));
+        assertThat(filtered, not(containsString("18375")));
+    }
+
+    @Test
+    public void testFilterObject() throws Exception {
+        String filtered = getFilter("cars") .filter(getResource("/cars-object.json"));
+        assertThat(filtered, not(containsString("Ford")));
+    }
+
+    @Test
+    public void testFilterArray() throws Exception {
+        String filtered = getFilter("cars") .filter(getResource("/cars-array.json"));
+        assertThat(filtered, not(containsString("Ford")));
+    }
+
+    @Test
+    public void testFilterHugeBodyObject1() throws Exception {
+        String string = getResource("/huge-sample.json");
+        String filtered = getFilter("name").filter(string);
+        assertThat(filtered, not(containsString("Pena Hudson")));
+        assertThat(filtered.length(), is(lessThan(string.length())));
+    }
+
+    @Test
+    public void testFilterHugeBodyObject2() throws Exception {
+        Set<String> remove = new HashSet<>();
+        remove.add("name");
+        String string = getResource("/huge-sample.json");
+        String filtered = getFilter(remove).filter("application/json", string);
+        assertThat(filtered, not(containsString("Pena Hudson")));
+        assertThat(filtered.length(), is(lessThan(string.length())));
+    }
+
+    @Test
+    public void doesNotFilterInvalidJson() throws Exception {
+        String valid = getResource("/cars-array.json").trim();
+        String invalid = valid.substring(0, valid.length() - 1);
+        String filtered = getFilter("cars").filter(invalid);
+        assertThat(filtered, containsString("Ford"));
+    }
+
+    @Test
+    public void doesNotFilterNonJson() throws Exception {
+        String valid = getResource("/cars-array.json").trim();
+        String invalid = valid.substring(0, valid.length() - 1);
+        String filtered = getFilter("cars").filter("application/xml", invalid);
+        assertThat(filtered, containsString("Ford"));
+    }    
+
+    private String getResource(String path) throws IOException {
+        final byte[] bytes = Files.readAllBytes(Paths.get("src/test/resources/" + path));
+        return new String(bytes, UTF_8);
+    }
+
+    public static JacksonJsonFieldBodyFilter getFilter(String ... fieldNames) {
+        return new JacksonJsonFieldBodyFilter(Arrays.asList(fieldNames), "XXX");
+    }
+
+    public static JacksonJsonFieldBodyFilter getFilter(Collection<String> fieldNames) {
+        return new JacksonJsonFieldBodyFilter(fieldNames , "XXX");
+    }
+
+}

logbook-json/src/test/resources/cars-array.json

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+{
+    "name":"John",
+    "age":30,
+    "cars": [
+        {"car1":"Ford"},
+        {"car2":"BMW"},
+        {"car3":"Fiat"}
+    ]
+ }

logbook-json/src/test/resources/cars-object.json

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+{
+    "name":"John",
+    "age":30,
+    "cars": {
+        "car1":"Ford",
+        "car2":"BMW",
+        "car3":"Fiat"
+    }
+ }

logbook-json/src/test/resources/user.json

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+{
+    "id": 1,
+    "customerNumber": 1234567,
+    "profileType": "S",
+    "status": "A",
+    "firstName": "My",
+    "surname": "Name",
+    "email": "someone@zalando.org",
+    "languagePreference": "NO",
+    "uuid": "658DE1D4BB4F3AC4E053020011AC1EC3"
+}