BAEL-1200 JavaPoet (#4500)

* Initial commit * Implement JavaPoet examples
2018-06-20 00:32:28 +02:00
parent 4109abebf9
commit d757050209
7 changed files with 362 additions and 0 deletions
@@ -0,0 +1,183 @@
+package com.baeldung.javapoet;
+
+import com.squareup.javapoet.ClassName;
+import com.squareup.javapoet.CodeBlock;
+import com.squareup.javapoet.FieldSpec;
+import com.squareup.javapoet.JavaFile;
+import com.squareup.javapoet.MethodSpec;
+import com.squareup.javapoet.ParameterSpec;
+import com.squareup.javapoet.ParameterizedTypeName;
+import com.squareup.javapoet.TypeName;
+import com.squareup.javapoet.TypeSpec;
+
+import javax.lang.model.element.Modifier;
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.IntStream;
+
+public class PersonGenerator {
+
+    private static final String FOUR_WHITESPACES = "    ";
+    private static final String PERSON_PACKAGE_NAME = "com.baeldung.javapoet.test.person";
+
+    private File outputFile;
+
+    public PersonGenerator() {
+        outputFile = new File(getOutputPath().toUri());
+    }
+
+    public static String getPersonPackageName() {
+        return PERSON_PACKAGE_NAME;
+    }
+
+    public Path getOutputPath() {
+        return Paths.get(new File(".").getAbsolutePath() + "/gensrc");
+    }
+
+    public FieldSpec getDefaultNameField() {
+        return FieldSpec
+          .builder(String.class, "DEFAULT_NAME")
+          .addModifiers(Modifier.PUBLIC, Modifier.STATIC, Modifier.FINAL)
+          .initializer("$S", "Alice")
+          .build();
+    }
+
+    public MethodSpec getSortByLengthMethod() {
+        return MethodSpec
+          .methodBuilder("sortByLength")
+          .addModifiers(Modifier.PUBLIC, Modifier.STATIC)
+          .addParameter(ParameterSpec
+            .builder(ParameterizedTypeName.get(ClassName.get(List.class), TypeName.get(String.class)), "strings")
+            .build())
+          .addStatement("$T.sort($N, $L)", Collections.class, "strings", getComparatorAnonymousClass())
+          .build();
+    }
+
+    public MethodSpec getPrintNameMultipleTimesMethod() {
+        return MethodSpec
+          .methodBuilder("printNameMultipleTimes")
+          .addModifiers(Modifier.PUBLIC)
+          .addCode(getPrintNameMultipleTimesLambdaImpl())
+          .build();
+    }
+
+    public CodeBlock getPrintNameMultipleTimesImpl() {
+        return CodeBlock
+          .builder()
+          .beginControlFlow("for (int i = $L; i < $L; i++)")
+          .addStatement("System.out.println(name)")
+          .endControlFlow()
+          .build();
+    }
+
+    public CodeBlock getPrintNameMultipleTimesLambdaImpl() {
+        return CodeBlock
+          .builder()
+          .addStatement("$T<$T> names = new $T<>()", List.class, String.class, ArrayList.class)
+          .addStatement("$T.range($L, $L).forEach(i -> names.add(name))", IntStream.class, 0, 10)
+          .addStatement("names.forEach(System.out::println)")
+          .build();
+    }
+
+    public TypeSpec getGenderEnum() {
+        return TypeSpec
+          .enumBuilder("Gender")
+          .addModifiers(Modifier.PUBLIC)
+          .addEnumConstant("MALE")
+          .addEnumConstant("FEMALE")
+          .addEnumConstant("UNSPECIFIED")
+          .build();
+    }
+
+    public TypeSpec getPersonInterface() {
+        return TypeSpec
+          .interfaceBuilder("Person")
+          .addModifiers(Modifier.PUBLIC)
+          .addField(getDefaultNameField())
+          .addMethod(MethodSpec
+            .methodBuilder("getName")
+            .addModifiers(Modifier.PUBLIC, Modifier.ABSTRACT)
+            .returns(String.class)
+            .build())
+          .addMethod(MethodSpec
+            .methodBuilder("getDefaultName")
+            .addModifiers(Modifier.PUBLIC, Modifier.DEFAULT)
+            .returns(String.class)
+            .addCode(CodeBlock
+              .builder()
+              .addStatement("return DEFAULT_NAME")
+              .build())
+            .build())
+          .build();
+    }
+
+    public TypeSpec getStudentClass() {
+        return TypeSpec
+          .classBuilder("Student")
+          .addSuperinterface(ClassName.get(PERSON_PACKAGE_NAME, "Person"))
+          .addModifiers(Modifier.PUBLIC)
+          .addField(FieldSpec
+            .builder(String.class, "name")
+            .addModifiers(Modifier.PRIVATE)
+            .build())
+          .addMethod(MethodSpec
+            .methodBuilder("getName")
+            .addAnnotation(Override.class)
+            .addModifiers(Modifier.PUBLIC)
+            .returns(String.class)
+            .addStatement("return this.name")
+            .build())
+          .addMethod(MethodSpec
+            .methodBuilder("setName")
+            .addParameter(String.class, "name")
+            .addModifiers(Modifier.PUBLIC)
+            .addStatement("this.name = name")
+            .build())
+          .addMethod(getPrintNameMultipleTimesMethod())
+          .addMethod(getSortByLengthMethod())
+          .build();
+    }
+
+    public TypeSpec getComparatorAnonymousClass() {
+        return TypeSpec
+          .anonymousClassBuilder("")
+          .addSuperinterface(ParameterizedTypeName.get(Comparator.class, String.class))
+          .addMethod(MethodSpec
+            .methodBuilder("compare")
+            .addModifiers(Modifier.PUBLIC)
+            .addAnnotation(Override.class)
+            .addParameter(String.class, "a")
+            .addParameter(String.class, "b")
+            .returns(int.class)
+            .addStatement("return a.length() - b.length()")
+            .build())
+          .build();
+    }
+
+    public void generateGenderEnum() throws IOException {
+        writeToOutputFile(getPersonPackageName(), getGenderEnum());
+    }
+
+    public void generatePersonInterface() throws IOException {
+        writeToOutputFile(getPersonPackageName(), getPersonInterface());
+    }
+
+    public void generateStudentClass() throws IOException {
+        writeToOutputFile(getPersonPackageName(), getStudentClass());
+    }
+
+    private void writeToOutputFile(String packageName, TypeSpec typeSpec) throws IOException {
+        JavaFile javaFile = JavaFile
+          .builder(packageName, typeSpec)
+          .indent(FOUR_WHITESPACES)
+          .build();
+        javaFile.writeTo(outputFile);
+    }
+
+}