Verify CSV headers are in the order as expected

src/main/java/com/fasterxml/jackson/dataformat/csv/CsvParser.java

@@ -838,8 +838,24 @@ protected void _readHeaderLine() throws IOException {
          */
 
         if (_schema.size() > 0 && !_schema.reordersColumns()) {
-            //noinspection StatementWithEmptyBody
-            while (_reader.nextString() != null) { /* does nothing */ }
+            if (_schema.strictHeaders()) {
+                String name;
+                for (CsvSchema.Column column : _schema._columns) {
+                    name = _reader.nextString();
+                    if (name == null) {
+                        _reportError(String.format("Missing header %s", column.getName()));
+                    } else if (!column.getName().equals(name)) {
+                        _reportError(String.format("Expected header %s, actual header %s", column.getName(), name));
+                    }
+                }
+                if ((name = _reader.nextString()) != null) {
+                    _reportError(String.format("Extra header %s", name));
+                }
+            }
+            else {
+                //noinspection StatementWithEmptyBody
+                while (_reader.nextString() != null) { /* does nothing */ }
+            }
             return;
         }
 

src/main/java/com/fasterxml/jackson/dataformat/csv/CsvSchema.java

@@ -83,6 +83,7 @@ public class CsvSchema
     protected final static int ENCODING_FEATURE_SKIP_FIRST_DATA_ROW = 0x0002;
     protected final static int ENCODING_FEATURE_ALLOW_COMMENTS = 0x0004;
     protected final static int ENCODING_FEATURE_REORDER_COLUMNS = 0x0008;
+    protected final static int ENCODING_FEATURE_STRICT_HEADERS = 0x0016;
 
     protected final static int DEFAULT_ENCODING_FEATURES = 0;
 
@@ -471,6 +472,22 @@ public Builder setReorderColumns(boolean b) {
             return this;
         }
 
+
+        /**
+         * Use in combination with setUseHeader.  When use header flag is
+         * is set, this setting will ensure the headers are in the order
+         * of the schema
+         *
+         * @param b         Enable / Disable this setting
+         * @return          This Builder instance
+         *
+         * @since 2.7
+         */
+        public Builder setStrictHeaders(boolean b) {
+            _feature(ENCODING_FEATURE_STRICT_HEADERS, b);
+            return this;
+        }
+
         /**
          * Method for specifying whether Schema should indicate that
          * the first line that is not a header (if header handling enabled)
@@ -804,6 +821,19 @@ public CsvSchema withColumnReordering(boolean state) {
         return _withFeature(ENCODING_FEATURE_REORDER_COLUMNS, state);
     }
 
+    /**
+     * Returns a clone of this instance by changing or setting the
+     * strict headers flag
+     *
+     * @param state     New value for setting
+     * @return          A copy of itself, ensuring the setting for
+     *                  the strict headers feature.
+     * @since 2.7
+     */
+    public CsvSchema withStrictColumns(boolean state) {
+        return _withFeature(ENCODING_FEATURE_STRICT_HEADERS, state);
+    }
+
     /**
      * Helper method for constructing and returning schema instance that
      * is similar to this one, except that it will be using header line.
@@ -1001,6 +1031,7 @@ public String getSchemaType() {
     public boolean reordersColumns() { return (_features & ENCODING_FEATURE_REORDER_COLUMNS) != 0; }
     public boolean skipsFirstDataRow() { return (_features & ENCODING_FEATURE_SKIP_FIRST_DATA_ROW) != 0; }
     public boolean allowsComments() { return (_features & ENCODING_FEATURE_ALLOW_COMMENTS) != 0; }
+    public boolean strictHeaders() { return (_features & ENCODING_FEATURE_STRICT_HEADERS) != 0; }
 
     /**
      * @deprecated Use {@link #usesHeader()} instead

src/test/java/com/fasterxml/jackson/dataformat/csv/deser/BasicParserTest.java

@@ -5,6 +5,7 @@
 import java.util.*;
 
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.core.JsonToken;
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.dataformat.csv.*;
@@ -328,4 +329,79 @@ public void testColumnReordering() throws IOException {
         assertEquals(JsonToken.END_OBJECT, parser.nextToken());
         parser.close();
     }
+
+    public void testColumnFailsOnOutOfOrder() throws IOException {
+        CsvFactory factory = new CsvFactory();
+        String CSV = "b,a,c\nvb,va,vc\n";
+
+        CsvSchema schema = CsvSchema.builder()
+                .addColumn("a")
+                .addColumn("b")
+                .addColumn("c")
+                .setLineSeparator('\n')
+                .setUseHeader(true)
+                .setStrictHeaders(true)
+                .build();
+
+        CsvParser parser = factory.createParser(CSV);
+        parser.setSchema(schema);
+
+        try {
+            parser.nextToken();
+            fail("Should have failed");
+        } catch (JsonProcessingException e) {
+            verifyException(e, "Expected header a, actual header b");
+        }
+        parser.close();
+    }
+
+    public void testColumnFailsOnTooFew() throws IOException {
+        CsvFactory factory = new CsvFactory();
+        String CSV = "a,b\nvb,va,vc\n";
+
+        CsvSchema schema = CsvSchema.builder()
+                .addColumn("a")
+                .addColumn("b")
+                .addColumn("c")
+                .setLineSeparator('\n')
+                .setUseHeader(true)
+                .setStrictHeaders(true)
+                .build();
+
+        CsvParser parser = factory.createParser(CSV);
+        parser.setSchema(schema);
+
+        try {
+            parser.nextToken();
+            fail("Should have failed");
+        } catch (JsonProcessingException e) {
+            verifyException(e, "Missing header c");
+        }
+        parser.close();
+    }
+
+    public void testColumnFailsOnTooMany() throws IOException {
+        CsvFactory factory = new CsvFactory();
+        String CSV = "a,b,c,d\nvb,va,vc\n";
+
+        CsvSchema schema = CsvSchema.builder()
+                .addColumn("a")
+                .addColumn("b")
+                .addColumn("c")
+                .setLineSeparator('\n')
+                .setUseHeader(true)
+                .setStrictHeaders(true)
+                .build();
+
+        CsvParser parser = factory.createParser(CSV);
+        parser.setSchema(schema);
+
+        try {
+            parser.nextToken();
+            fail("Should have failed");
+        } catch (JsonProcessingException e) {
+            verifyException(e, "Extra header d");
+        }
+        parser.close();
+    }
 }