Avoid generating uncompilable response body in Spring's API template

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/SpringCodegen.java

@@ -6,6 +6,8 @@
 import io.swagger.codegen.languages.features.BeanValidationFeatures;
 import io.swagger.codegen.languages.features.NotNullAnnotationFeatures;
 import io.swagger.codegen.languages.features.OptionalFeatures;
+import io.swagger.codegen.mustache.SplitStringLambda;
+import io.swagger.codegen.mustache.TrimWhitespaceLambda;
 import io.swagger.models.Operation;
 import io.swagger.models.Path;
 import io.swagger.models.Swagger;
@@ -361,6 +363,10 @@ public void execute(Template.Fragment fragment, Writer writer) throws IOExceptio
                 writer.write(fragment.execute().replaceAll("\\r|\\n", ""));
             }
         });
+
+        additionalProperties.put("lambdaTrimWhitespace", new TrimWhitespaceLambda());
+
+        additionalProperties.put("lambdaSplitString", new SplitStringLambda());
     }
 
     @Override

modules/swagger-codegen/src/main/java/io/swagger/codegen/mustache/SplitStringLambda.java

@@ -0,0 +1,86 @@
+package io.swagger.codegen.mustache;
+
+import java.io.IOException;
+import java.io.Writer;
+
+import com.samskivert.mustache.Mustache;
+import com.samskivert.mustache.Template.Fragment;
+
+/**
+ * Splits long fragments into smaller strings and uses a StringBuilder to merge
+ * them back.
+ *
+ * Register:
+ *
+ * <pre>
+ * additionalProperties.put("lambdaSplitString", new SplitStringLambda());
+ * </pre>
+ *
+ * Use:
+ *
+ * <pre>
+ * {{#lambdaSplitString}}{{summary}}{{/lambdaSplitString}}
+ * </pre>
+ */
+public class SplitStringLambda implements Mustache.Lambda {
+    private static final int DEFAULT_MAX_LENGTH = 65535;
+
+    private static final String SPLIT_INIT = "new StringBuilder(%d)";
+
+    private static final String SPLIT_PART = ".append(\"%s\")";
+
+    private static final String SPLIT_SUFFIX = ".toString()";
+
+    private final int maxLength;
+
+    public SplitStringLambda() {
+        this(DEFAULT_MAX_LENGTH);
+    }
+
+    public SplitStringLambda(int maxLength) {
+        this.maxLength = maxLength;
+    }
+
+    @Override
+    public void execute(Fragment fragment, Writer writer) throws IOException {
+        String input = fragment.execute();
+        int inputLength = input.length();
+
+        StringBuilder builder = new StringBuilder();
+        if (inputLength > maxLength) {
+
+            // Initialize a StringBuilder
+            builder.append(String.format(SPLIT_INIT, inputLength));
+
+            int currentPosition = 0;
+            int currentStringLength = 0;
+            char currentLastChar = '\\';
+
+            // Split input into parts of at most maxLength and not ending with an escape character
+            // Append each part to the StringBuilder
+            while (currentPosition + maxLength < input.length()) {
+                currentStringLength = maxLength;
+                currentLastChar = input.charAt(currentPosition + currentStringLength - 1);
+                if (currentLastChar == '\\') {
+                    --currentStringLength;
+                }
+
+                builder.append(String.format(SPLIT_PART, input.substring(currentPosition, currentPosition + currentStringLength)));
+                currentPosition += currentStringLength;
+            }
+
+            // Append last part if necessary
+            if (currentPosition < input.length()) {
+                builder.append(String.format(SPLIT_PART, input.substring(currentPosition)));
+            }
+
+            // Close the builder and merge everything back to a string
+            builder.append(SPLIT_SUFFIX);
+        } else {
+            builder.append(String.format("\"%s\"", input));
+        }
+
+        writer.write(builder.toString());
+    }
+
+}

modules/swagger-codegen/src/main/java/io/swagger/codegen/mustache/TrimWhitespaceLambda.java

@@ -0,0 +1,34 @@
+package io.swagger.codegen.mustache;
+
+import java.io.IOException;
+import java.io.Writer;
+
+import com.samskivert.mustache.Mustache;
+import com.samskivert.mustache.Template.Fragment;
+
+/**
+ * Replaces duplicate whitespace characters in a fragment with single space.
+ *
+ * Register:
+ *
+ * <pre>
+ * additionalProperties.put("lambdaTrimWhitespace", new TrimWhitespaceLambda());
+ * </pre>
+ *
+ * Use:
+ *
+ * <pre>
+ * {{#lambdaTrimWhitespace}}{{summary}}{{/lambdaTrimWhitespace}}
+ * </pre>
+ */
+public class TrimWhitespaceLambda implements Mustache.Lambda {
+    private static final String SINGLE_SPACE = " ";
+
+    private static final String WHITESPACE_REGEX = "\\s+";
+
+    @Override
+    public void execute(Fragment fragment, Writer writer) throws IOException {
+        writer.write(fragment.execute().replaceAll(WHITESPACE_REGEX, SINGLE_SPACE));
+    }
+
+}

modules/swagger-codegen/src/main/resources/JavaSpring/api.mustache

@@ -117,7 +117,8 @@ public interface {{classname}} {
         {{#examples}}
             if (getAcceptHeader().get().contains("{{{contentType}}}")) {
                 try {
-                    return {{#async}}CompletableFuture.completedFuture({{/async}}new ResponseEntity<>(getObjectMapper().get().readValue("{{#lambdaRemoveLineBreak}}{{#lambdaEscapeDoubleQuote}}{{{example}}}{{/lambdaEscapeDoubleQuote}}{{/lambdaRemoveLineBreak}}", {{>exampleReturnTypes}}.class), HttpStatus.NOT_IMPLEMENTED){{#async}}){{/async}};
+                    String exampleString = {{#lambdaSplitString}}{{#lambdaRemoveLineBreak}}{{#lambdaEscapeDoubleQuote}}{{#lambdaTrimWhitespace}}{{{example}}}{{/lambdaTrimWhitespace}}{{/lambdaEscapeDoubleQuote}}{{/lambdaRemoveLineBreak}}{{/lambdaSplitString}};
+                    return {{#async}}CompletableFuture.completedFuture({{/async}}new ResponseEntity<>(getObjectMapper().get().readValue(exampleString, {{>exampleReturnTypes}}.class), HttpStatus.NOT_IMPLEMENTED){{#async}}){{/async}};
                 } catch (IOException e) {
                     log.error("Couldn't serialize response for content type {{{contentType}}}", e);
                     return {{#async}}CompletableFuture.completedFuture({{/async}}new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR){{#async}}){{/async}};
@@ -136,4 +137,4 @@ public interface {{classname}} {
 
 {{/operation}}
 }
-{{/operations}}
+{{/operations}}

modules/swagger-codegen/src/test/java/io/swagger/codegen/mustache/SplitStringLambdaTest.java

@@ -0,0 +1,85 @@
+package io.swagger.codegen.mustache;
+
+import static org.mockito.Mockito.when;
+import static org.testng.Assert.assertEquals;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.MockitoAnnotations;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+import com.samskivert.mustache.Template.Fragment;
+
+public class SplitStringLambdaTest {
+    private static final String INPUT_STRING = "1112223334";
+
+    private static final Map<Integer, String> EXPECTED_OUTPUTS;
+    static {
+        EXPECTED_OUTPUTS = new HashMap<>();
+        EXPECTED_OUTPUTS.put(2,
+                String.format(
+                        "new StringBuilder(%d).append(\"11\").append(\"12\").append(\"22\").append(\"33\").append(\"34\").toString()",
+                        INPUT_STRING.length()));
+        EXPECTED_OUTPUTS.put(3,
+                String.format(
+                        "new StringBuilder(%d).append(\"111\").append(\"222\").append(\"333\").append(\"4\").toString()",
+                        INPUT_STRING.length()));
+    }
+
+    private static final String INPUT_QUOTED_STRING = "1\\\"11\\\"2223\\\"334";
+    private static final String INPUT_QUOTED_OUTPUT = String.format(
+            "new StringBuilder(%d).append(\"1\\\"\").append(\"11\").append(\"\\\"2\").append(\"223\").append(\"\\\"3\").append(\"34\").toString()",
+            INPUT_QUOTED_STRING.length());
+
+    @Mock
+    private Fragment fragment;
+
+    @BeforeMethod
+    public void init() {
+        MockitoAnnotations.initMocks(this);
+    }
+
+    @AfterMethod
+    public void reset() {
+        Mockito.reset(fragment);
+    }
+
+    private void testString(String input, int maxLength, String expected) throws IOException {
+        when(fragment.execute()).thenReturn(input);
+
+        StringWriter output = new StringWriter();
+        new SplitStringLambda(maxLength).execute(fragment, output);
+        assertEquals(output.toString(), expected);
+    }
+
+    @Test
+    public void testSplitGroupsOf2() throws IOException {
+        int maxLength = 2;
+        testString(INPUT_STRING, maxLength, EXPECTED_OUTPUTS.get(maxLength));
+    }
+
+    @Test
+    public void testSplitGroupsOf3() throws IOException {
+        int maxLength = 3;
+        testString(INPUT_STRING, maxLength, EXPECTED_OUTPUTS.get(maxLength));
+    }
+
+    @Test
+    public void testSplitQuotedString() throws IOException {
+        int maxLength = 3;
+        testString(INPUT_QUOTED_STRING, maxLength, INPUT_QUOTED_OUTPUT);
+    }
+
+    @Test
+    public void testShortString() throws IOException {
+        testString(INPUT_STRING, INPUT_STRING.length(), String.format("\"%s\"", INPUT_STRING));
+    }
+
+}

modules/swagger-codegen/src/test/java/io/swagger/codegen/mustache/TrimWhitespaceLambdaTest.java

@@ -0,0 +1,42 @@
+package io.swagger.codegen.mustache;
+
+import static org.mockito.Mockito.when;
+import static org.testng.Assert.assertEquals;
+
+import java.io.IOException;
+import java.io.StringWriter;
+
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.MockitoAnnotations;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+import com.samskivert.mustache.Template.Fragment;
+
+public class TrimWhitespaceLambdaTest {
+
+    @Mock
+    private Fragment fragment;
+
+    @BeforeMethod
+    public void init() {
+        MockitoAnnotations.initMocks(this);
+    }
+
+    @AfterMethod
+    public void reset() {
+        Mockito.reset(fragment);
+    }
+
+    @Test
+    public void testTrimWhitespace() throws IOException {
+        when(fragment.execute()).thenReturn("\t a  b\t\tc \t");
+
+        StringWriter output = new StringWriter();
+        new TrimWhitespaceLambda().execute(fragment, output);
+        assertEquals(output.toString(), " a b c ");
+    }
+
+}