javapoet README

The project's README from github.com/square/javapoet. As one markdown file: README.md.

JavaPoet

JavaPoet is a Java API for generating .java source files.

Source file generation can be useful when doing things such as annotation processing or interacting with metadata files (e.g., database schemas, protocol formats). By generating code, you eliminate the need to write boilerplate while also keeping a single source of truth for the metadata.

Deprecated

As of 2020-10-10, Square's JavaPoet project is deprecated. We're proud of our work but we haven't kept up on maintaining it.

If you'd like an alternative that supports the latest Java language features, one option is Palantir's JavaPoet.

To switch to that project, you'll need new Maven coordinates:

- javapoet = { module = "com.squareup:javapoet", version = "1.13.0" }
+ javapoet = { module = "com.palantir.javapoet:javapoet", version = "0.5.0" }

And new imports:

sed -i "" \
  's/com.squareup.javapoet.\([A-Za-z]*\)/com.palantir.javapoet.\1/g' \
  `find . -name "*.kt" -or -name "*.java"`

And you might need to track some API changes where fields became functions:

- javaFile.packageName
+ javaFile.packageName()

Example

Here's a (boring) HelloWorld class:

package com.example.helloworld;

public final class HelloWorld {
  public static void main(String[] args) {
    System.out.println("Hello, JavaPoet!");
  }
}

And this is the (exciting) code to generate it with JavaPoet:

MethodSpec main = MethodSpec.methodBuilder("main")
    .addModifiers(Modifier.PUBLIC, Modifier.STATIC)
    .returns(void.class)
    .addParameter(String[].class, "args")
    .addStatement("$T.out.println($S)", System.class, "Hello, JavaPoet!")
    .build();

TypeSpec helloWorld = TypeSpec.classBuilder("HelloWorld")
    .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
    .addMethod(main)
    .build();

JavaFile javaFile = JavaFile.builder("com.example.helloworld", helloWorld)
    .build();

javaFile.writeTo(System.out);

To declare the main method, we've created a MethodSpec "main" configured with modifiers, return type, parameters and code statements. We add the main method to a HelloWorld class, and then add that to a HelloWorld.java file.

In this case we write the file to System.out, but we could also get it as a string (JavaFile.toString()) or write it to the file system (JavaFile.writeTo()).

The Javadoc catalogs the complete JavaPoet API, which we explore below.

Code & Control Flow

Most of JavaPoet's API uses plain old immutable Java objects. There's also builders, method chaining and varargs to make the API friendly. JavaPoet offers models for classes & interfaces (TypeSpec), fields (FieldSpec), methods & constructors (MethodSpec), parameters (ParameterSpec) and annotations (AnnotationSpec).

But the body of methods and constructors is not modeled. There's no expression class, no statement class or syntax tree nodes. Instead, JavaPoet uses strings for code blocks:

MethodSpec main = MethodSpec.methodBuilder("main")
    .addCode(""
        + "int total = 0;\n"
        + "for (int i = 0; i < 10; i++) {\n"
        + "  total += i;\n"
        + "}\n")
    .build();

Which generates this:

void main() {
  int total = 0;
  for (int i = 0; i < 10; i++) {
    total += i;
  }
}

The manual semicolons, line wrapping, and indentation are tedious and so JavaPoet offers APIs to make it easier. There's addStatement() which takes care of semicolons and newline, and beginControlFlow() + endControlFlow() which are used together for braces, newlines, and indentation:

MethodSpec main = MethodSpec.methodBuilder("main")
    .addStatement("int total = 0")
    .beginControlFlow("for (int i = 0; i < 10; i++)")
    .addStatement("total += i")
    .endControlFlow()
    .build();

This example is lame because the generated code is constant! Suppose instead of just adding 0 to 10, we want to make the operation and range configurable. Here's a method that generates a method:

private MethodSpec computeRange(String name, int from, int to, String op) {
  return MethodSpec.methodBuilder(name)
      .returns(int.class)
      .addStatement("int result = 1")
      .beginControlFlow("for (int i = " + from + "; i < " + to + "; i++)")
      .addStatement("result = result " + op + " i")
      .endControlFlow()
      .addStatement("return result")
      .build();
}

And here's what we get when we call computeRange("multiply10to20", 10, 20, "*"):

int multiply10to20() {
  int result = 1;
  for (int i = 10; i < 20; i++) {
    result = result * i;
  }
  return result;
}

Methods generating methods! And since JavaPoet generates source instead of bytecode, you can read through it to make sure it's right.

Some control flow statements, such as if/else, can have unlimited control flow possibilities. You can handle those options using nextControlFlow():

MethodSpec main = MethodSpec.methodBuilder("main")
    .addStatement("long now = $T.currentTimeMillis()", System.class)
    .beginControlFlow("if ($T.currentTimeMillis() < now)", System.class)
    .addStatement("$T.out.println($S)", System.class, "Time travelling, woo hoo!")
    .nextControlFlow("else if ($T.currentTimeMillis() == now)", System.class)
    .addStatement("$T.out.println($S)", System.class, "Time stood still!")
    .nextControlFlow("else")
    .addStatement("$T.out.println($S)", System.class, "Ok, time still moving forward")
    .endControlFlow()
    .build();

Which generates:

void main() {
  long now = System.currentTimeMillis();
  if (System.currentTimeMillis() < now)  {
    System.out.println("Time travelling, woo hoo!");
  } else if (System.currentTimeMillis() == now) {
    System.out.println("Time stood still!");
  } else {
    System.out.println("Ok, time still moving forward");
  }
}

Catching exceptions using try/catch is also a use case for nextControlFlow():

MethodSpec main = MethodSpec.methodBuilder("main")
    .beginControlFlow("try")
    .addStatement("throw new Exception($S)", "Failed")
    .nextControlFlow("catch ($T e)", Exception.class)
    .addStatement("throw new $T(e)", RuntimeException.class)
    .endControlFlow()
    .build();

Which produces:

void main() {
  try {
    throw new Exception("Failed");
  } catch (Exception e) {
    throw new RuntimeException(e);
  }
}

$L for Literals

The string-concatenation in calls to beginControlFlow() and addStatement is distracting. Too many operators. To address this, JavaPoet offers a syntax inspired-by but incompatible-with String.format(). It accepts $L to emit a literal value in the output. This works just like Formatter's %s:

private MethodSpec computeRange(String name, int from, int to, String op) {
  return MethodSpec.methodBuilder(name)
      .returns(int.class)
      .addStatement("int result = 0")
      .beginControlFlow("for (int i = $L; i < $L; i++)", from, to)
      .addStatement("result = result $L i", op)
      .endControlFlow()
      .addStatement("return result")
      .build();
}

Literals are emitted directly to the output code with no escaping. Arguments for literals may be strings, primitives, and a few JavaPoet types described below.

$S for Strings

When emitting code that includes string literals, we can use $S to emit a string, complete with wrapping quotation marks and escaping. Here's a program that emits 3 methods, each of which returns its own name:

public static void main(String[] args) throws Exception {
  TypeSpec helloWorld = TypeSpec.classBuilder("HelloWorld")
      .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
      .addMethod(whatsMyName("slimShady"))
      .addMethod(whatsMyName("eminem"))
      .addMethod(whatsMyName("marshallMathers"))
      .build();

  JavaFile javaFile = JavaFile.builder("com.example.helloworld", helloWorld)
      .build();

  javaFile.writeTo(System.out);
}

private static MethodSpec whatsMyName(String name) {
  return MethodSpec.methodBuilder(name)
      .returns(String.class)
      .addStatement("return $S", name)
      .build();
}

In this case, using $S gives us quotation marks:

public final class HelloWorld {
  String slimShady() {
    return "slimShady";
  }

  String eminem() {
    return "eminem";
  }

  String marshallMathers() {
    return "marshallMathers";
  }
}

$T for Types

We Java programmers love our types: they make our code easier to understand. And JavaPoet is on board. It has rich built-in support for types, including automatic generation of import statements. Just use $T to reference types:

MethodSpec today = MethodSpec.methodBuilder("today")
    .returns(Date.class)
    .addStatement("return new $T()", Date.class)
    .build();

TypeSpec helloWorld = TypeSpec.classBuilder("HelloWorld")
    .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
    .addMethod(today)
    .build();

JavaFile javaFile = JavaFile.builder("com.example.helloworld", helloWorld)
    .build();

javaFile.writeTo(System.out);

That generates the following .java file, complete with the necessary import:

package com.example.helloworld;

import java.util.Date;

public final class HelloWorld {
  Date today() {
    return new Date();
  }
}

We passed Date.class to reference a class that just-so-happens to be available when we're generating code. This doesn't need to be the case. Here's a similar example, but this one references a class that doesn't exist (yet):

ClassName hoverboard = ClassName.get("com.mattel", "Hoverboard");

MethodSpec today = MethodSpec.methodBuilder("tomorrow")
    .returns(hoverboard)
    .addStatement("return new $T()", hoverboard)
    .build();

And that not-yet-existent class is imported as well:

package com.example.helloworld;

import com.mattel.Hoverboard;

public final class HelloWorld {
  Hoverboard tomorrow() {
    return new Hoverboard();
  }
}

The ClassName type is very important, and you'll need it frequently when you're using JavaPoet. It can identify any declared class. Declared types are just the beginning of Java's rich type system: we also have arrays, parameterized types, wildcard types, and type variables. JavaPoet has classes for building each of these:

ClassName hoverboard = ClassName.get("com.mattel", "Hoverboard");
ClassName list = ClassName.get("java.util", "List");
ClassName arrayList = ClassName.get("java.util", "ArrayList");
TypeName listOfHoverboards = ParameterizedTypeName.get(list, hoverboard);

MethodSpec beyond = MethodSpec.methodBuilder("beyond")
    .returns(listOfHoverboards)
    .addStatement("$T result = new $T<>()", listOfHoverboards, arrayList)
    .addStatement("result.add(new $T())", hoverboard)
    .addStatement("result.add(new $T())", hoverboard)
    .addStatement("result.add(new $T())", hoverboard)
    .addStatement("return result")
    .build();

JavaPoet will decompose each type and import its components where possible.

package com.example.helloworld;

import com.mattel.Hoverboard;
import java.util.ArrayList;
import java.util.List;

public final class HelloWorld {
  List<Hoverboard> beyond() {
    List<Hoverboard> result = new ArrayList<>();
    result.add(new Hoverboard());
    result.add(new Hoverboard());
    result.add(new Hoverboard());
    return result;
  }
}

Import static

JavaPoet supports import static. It does it via explicitly collecting type member names. Let's enhance the previous example with some static sugar:

...
ClassName namedBoards = ClassName.get("com.mattel", "Hoverboard", "Boards");

MethodSpec beyond = MethodSpec.methodBuilder("beyond")
    .returns(listOfHoverboards)
    .addStatement("$T result = new $T<>()", listOfHoverboards, arrayList)
    .addStatement("result.add($T.createNimbus(2000))", hoverboard)
    .addStatement("result.add($T.createNimbus(\"2001\"))", hoverboard)
    .addStatement("result.add($T.createNimbus($T.THUNDERBOLT))", hoverboard, namedBoards)
    .addStatement("$T.sort(result)", Collections.class)
    .addStatement("return result.isEmpty() ? $T.emptyList() : result", Collections.class)
    .build();

TypeSpec hello = TypeSpec.classBuilder("HelloWorld")
    .addMethod(beyond)
    .build();

JavaFile.builder("com.example.helloworld", hello)
    .addStaticImport(hoverboard, "createNimbus")
    .addStaticImport(namedBoards, "*")
    .addStaticImport(Collections.class, "*")
    .build();

JavaPoet will first add your import static block to the file as configured, match and mangle all calls accordingly and also import all other types as needed.

package com.example.helloworld;

import static com.mattel.Hoverboard.Boards.*;
import static com.mattel.Hoverboard.createNimbus;
import static java.util.Collections.*;

import com.mattel.Hoverboard;
import java.util.ArrayList;
import java.util.List;

class HelloWorld {
  List<Hoverboard> beyond() {
    List<Hoverboard> result = new ArrayList<>();
    result.add(createNimbus(2000));
    result.add(createNimbus("2001"));
    result.add(createNimbus(THUNDERBOLT));
    sort(result);
    return result.isEmpty() ? emptyList() : result;
  }
}

$N for Names

Generated code is often self-referential. Use $N to refer to another generated declaration by its name. Here's a method that calls another:

public String byteToHex(int b) {
  char[] result = new char[2];
  result[0] = hexDigit((b >>> 4) & 0xf);
  result[1] = hexDigit(b & 0xf);
  return new String(result);
}

public char hexDigit(int i) {
  return (char) (i < 10 ? i + '0' : i - 10 + 'a');
}

When generating the code above, we pass the hexDigit() method as an argument to the byteToHex() method using $N:

MethodSpec hexDigit = MethodSpec.methodBuilder("hexDigit")
    .addParameter(int.class, "i")
    .returns(char.class)
    .addStatement("return (char) (i < 10 ? i + '0' : i - 10 + 'a')")
    .build();

MethodSpec byteToHex = MethodSpec.methodBuilder("byteToHex")
    .addParameter(int.class, "b")
    .returns(String.class)
    .addStatement("char[] result = new char[2]")
    .addStatement("result[0] = $N((b >>> 4) & 0xf)", hexDigit)
    .addStatement("result[1] = $N(b & 0xf)", hexDigit)
    .addStatement("return new String(result)")
    .build();

Code block format strings

Code blocks may specify the values for their placeholders in a few ways. Only one style may be used for each operation on a code block.

Relative Arguments

Pass an argument value for each placeholder in the format string to CodeBlock.add(). In each example, we generate code to say "I ate 3 tacos"

CodeBlock.builder().add("I ate $L $L", 3, "tacos")

Positional Arguments

Place an integer index (1-based) before the placeholder in the format string to specify which argument to use.

CodeBlock.builder().add("I ate $2L $1L", "tacos", 3)

Named Arguments

Use the syntax $argumentName:X where X is the format character and call CodeBlock.addNamed() with a map containing all argument keys in the format string. Argument names use characters in a-z, A-Z, 0-9, and _, and must start with a lowercase character.

Map<String, Object> map = new LinkedHashMap<>();
map.put("food", "tacos");
map.put("count", 3);
CodeBlock.builder().addNamed("I ate $count:L $food:L", map)

Methods

All of the above methods have a code body. Use Modifiers.ABSTRACT to get a method without any body. This is only legal if the enclosing class is either abstract or an interface.

MethodSpec flux = MethodSpec.methodBuilder("flux")
    .addModifiers(Modifier.ABSTRACT, Modifier.PROTECTED)
    .build();

TypeSpec helloWorld = TypeSpec.classBuilder("HelloWorld")
    .addModifiers(Modifier.PUBLIC, Modifier.ABSTRACT)
    .addMethod(flux)
    .build();

Which generates this:

public abstract class HelloWorld {
  protected abstract void flux();
}

The other modifiers work where permitted. Note that when specifying modifiers, JavaPoet uses javax.lang.model.element.Modifier, a class that is not available on Android. This limitation applies to code-generating-code only; the output code runs everywhere: JVMs, Android, and GWT.

Methods also have parameters, exceptions, varargs, Javadoc, annotations, type variables, and a return type. All of these are configured with MethodSpec.Builder.

Constructors

MethodSpec is a slight misnomer; it can also be used for constructors:

MethodSpec flux = MethodSpec.constructorBuilder()
    .addModifiers(Modifier.PUBLIC)
    .addParameter(String.class, "greeting")
    .addStatement("this.$N = $N", "greeting", "greeting")
    .build();

TypeSpec helloWorld = TypeSpec.classBuilder("HelloWorld")
    .addModifiers(Modifier.PUBLIC)
    .addField(String.class, "greeting", Modifier.PRIVATE, Modifier.FINAL)
    .addMethod(flux)
    .build();

Which generates this:

public class HelloWorld {
  private final String greeting;

  public HelloWorld(String greeting) {
    this.greeting = greeting;
  }
}

For the most part, constructors work just like methods. When emitting code, JavaPoet will place constructors before methods in the output file.

Parameters

Declare parameters on methods and constructors with either ParameterSpec.builder() or MethodSpec's convenient addParameter() API:

ParameterSpec android = ParameterSpec.builder(String.class, "android")
    .addModifiers(Modifier.FINAL)
    .build();

MethodSpec welcomeOverlords = MethodSpec.methodBuilder("welcomeOverlords")
    .addParameter(android)
    .addParameter(String.class, "robot", Modifier.FINAL)
    .build();

Though the code above to generate android and robot parameters is different, the output is the same:

void welcomeOverlords(final String android, final String robot) {
}

The extended Builder form is necessary when the parameter has annotations (such as @Nullable).

Fields

Like parameters, fields can be created either with builders or by using convenient helper methods:

FieldSpec android = FieldSpec.builder(String.class, "android")
    .addModifiers(Modifier.PRIVATE, Modifier.FINAL)
    .build();

TypeSpec helloWorld = TypeSpec.classBuilder("HelloWorld")
    .addModifiers(Modifier.PUBLIC)
    .addField(android)
    .addField(String.class, "robot", Modifier.PRIVATE, Modifier.FINAL)
    .build();

Which generates:

public class HelloWorld {
  private final String android;

  private final String robot;
}

The extended Builder form is necessary when a field has Javadoc, annotations, or a field initializer. Field initializers use the same String.format()-like syntax as the code blocks above:

FieldSpec android = FieldSpec.builder(String.class, "android")
    .addModifiers(Modifier.PRIVATE, Modifier.FINAL)
    .initializer("$S + $L", "Lollipop v.", 5.0d)
    .build();

Which generates:

private final String android = "Lollipop v." + 5.0;

Interfaces

JavaPoet has no trouble with interfaces. Note that interface methods must always be PUBLIC ABSTRACT and interface fields must always be PUBLIC STATIC FINAL. These modifiers are necessary when defining the interface:

TypeSpec helloWorld = TypeSpec.interfaceBuilder("HelloWorld")
    .addModifiers(Modifier.PUBLIC)
    .addField(FieldSpec.builder(String.class, "ONLY_THING_THAT_IS_CONSTANT")
        .addModifiers(Modifier.PUBLIC, Modifier.STATIC, Modifier.FINAL)
        .initializer("$S", "change")
        .build())
    .addMethod(MethodSpec.methodBuilder("beep")
        .addModifiers(Modifier.PUBLIC, Modifier.ABSTRACT)
        .build())
    .build();

But these modifiers are omitted when the code is generated. These are the defaults so we don't need to include them for javac's benefit!

public interface HelloWorld {
  String ONLY_THING_THAT_IS_CONSTANT = "change";

  void beep();
}

Enums

Use enumBuilder to create the enum type, and addEnumConstant() for each value:

TypeSpec helloWorld = TypeSpec.enumBuilder("Roshambo")
    .addModifiers(Modifier.PUBLIC)
    .addEnumConstant("ROCK")
    .addEnumConstant("SCISSORS")
    .addEnumConstant("PAPER")
    .build();

To generate this:

public enum Roshambo {
  ROCK,

  SCISSORS,

  PAPER
}

Fancy enums are supported, where the enum values override methods or call a superclass constructor. Here's a comprehensive example:

TypeSpec helloWorld = TypeSpec.enumBuilder("Roshambo")
    .addModifiers(Modifier.PUBLIC)
    .addEnumConstant("ROCK", TypeSpec.anonymousClassBuilder("$S", "fist")
        .addMethod(MethodSpec.methodBuilder("toString")
            .addAnnotation(Override.class)
            .addModifiers(Modifier.PUBLIC)
            .addStatement("return $S", "avalanche!")
            .returns(String.class)
            .build())
        .build())
    .addEnumConstant("SCISSORS", TypeSpec.anonymousClassBuilder("$S", "peace")
        .build())
    .addEnumConstant("PAPER", TypeSpec.anonymousClassBuilder("$S", "flat")
        .build())
    .addField(String.class, "handsign", Modifier.PRIVATE, Modifier.FINAL)
    .addMethod(MethodSpec.constructorBuilder()
        .addParameter(String.class, "handsign")
        .addStatement("this.$N = $N", "handsign", "handsign")
        .build())
    .build();

Which generates this:

public enum Roshambo {
  ROCK("fist") {
    @Override
    public String toString() {
      return "avalanche!";
    }
  },

  SCISSORS("peace"),

  PAPER("flat");

  private final String handsign;

  Roshambo(String handsign) {
    this.handsign = handsign;
  }
}

Anonymous Inner Classes

In the enum code, we used TypeSpec.anonymousInnerClass(). Anonymous inner classes can also be used in code blocks. They are values that can be referenced with $L:

TypeSpec comparator = TypeSpec.anonymousClassBuilder("")
    .addSuperinterface(ParameterizedTypeName.get(Comparator.class, String.class))
    .addMethod(MethodSpec.methodBuilder("compare")
        .addAnnotation(Override.class)
        .addModifiers(Modifier.PUBLIC)
        .addParameter(String.class, "a")
        .addParameter(String.class, "b")
        .returns(int.class)
        .addStatement("return $N.length() - $N.length()", "a", "b")
        .build())
    .build();

TypeSpec helloWorld = TypeSpec.classBuilder("HelloWorld")
    .addMethod(MethodSpec.methodBuilder("sortByLength")
        .addParameter(ParameterizedTypeName.get(List.class, String.class), "strings")
        .addStatement("$T.sort($N, $L)", Collections.class, "strings", comparator)
        .build())
    .build();

This generates a method that contains a class that contains a method:

void sortByLength(List<String> strings) {
  Collections.sort(strings, new Comparator<String>() {
    @Override
    public int compare(String a, String b) {
      return a.length() - b.length();
    }
  });
}

One particularly tricky part of defining anonymous inner classes is the arguments to the superclass constructor. In the above code we're passing the empty string for no arguments: TypeSpec.anonymousClassBuilder(""). To pass different parameters use JavaPoet's code block syntax with commas to separate arguments.

Annotations

Simple annotations are easy:

MethodSpec toString = MethodSpec.methodBuilder("toString")
    .addAnnotation(Override.class)
    .returns(String.class)
    .addModifiers(Modifier.PUBLIC)
    .addStatement("return $S", "Hoverboard")
    .build();

Which generates this method with an @Override annotation:

  @Override
  public String toString() {
    return "Hoverboard";
  }

Use AnnotationSpec.builder() to set properties on annotations:

MethodSpec logRecord = MethodSpec.methodBuilder("recordEvent")
    .addModifiers(Modifier.PUBLIC, Modifier.ABSTRACT)
    .addAnnotation(AnnotationSpec.builder(Headers.class)
        .addMember("accept", "$S", "application/json; charset=utf-8")
        .addMember("userAgent", "$S", "Square Cash")
        .build())
    .addParameter(LogRecord.class, "logRecord")
    .returns(LogReceipt.class)
    .build();

Which generates this annotation with accept and userAgent properties:

@Headers(
    accept = "application/json; charset=utf-8",
    userAgent = "Square Cash"
)
LogReceipt recordEvent(LogRecord logRecord);

When you get fancy, annotation values can be annotations themselves. Use $L for embedded annotations:

MethodSpec logRecord = MethodSpec.methodBuilder("recordEvent")
    .addModifiers(Modifier.PUBLIC, Modifier.ABSTRACT)
    .addAnnotation(AnnotationSpec.builder(HeaderList.class)
        .addMember("value", "$L", AnnotationSpec.builder(Header.class)
            .addMember("name", "$S", "Accept")
            .addMember("value", "$S", "application/json; charset=utf-8")
            .build())
        .addMember("value", "$L", AnnotationSpec.builder(Header.class)
            .addMember("name", "$S", "User-Agent")
            .addMember("value", "$S", "Square Cash")
            .build())
        .build())
    .addParameter(LogRecord.class, "logRecord")
    .returns(LogReceipt.class)
    .build();

Which generates this:

@HeaderList({
    @Header(name = "Accept", value = "application/json; charset=utf-8"),
    @Header(name = "User-Agent", value = "Square Cash")
})
LogReceipt recordEvent(LogRecord logRecord);

Note that you can call addMember() multiple times with the same property name to populate a list of values for that property.

Javadoc

Fields, methods and types can be documented with Javadoc:

MethodSpec dismiss = MethodSpec.methodBuilder("dismiss")
    .addJavadoc("Hides {@code message} from the caller's history. Other\n"
        + "participants in the conversation will continue to see the\n"
        + "message in their own history unless they also delete it.\n")
    .addJavadoc("\n")
    .addJavadoc("<p>Use {@link #delete($T)} to delete the entire\n"
        + "conversation for all participants.\n", Conversation.class)
    .addModifiers(Modifier.PUBLIC, Modifier.ABSTRACT)
    .addParameter(Message.class, "message")
    .build();

Which generates this:

  /**
   * Hides {@code message} from the caller's history. Other
   * participants in the conversation will continue to see the
   * message in their own history unless they also delete it.
   *
   * <p>Use {@link #delete(Conversation)} to delete the entire
   * conversation for all participants.
   */
  void dismiss(Message message);

Use $T when referencing types in Javadoc to get automatic imports.

Download

Download the latest .jar or depend via Maven:

<dependency>
  <groupId>com.squareup</groupId>
  <artifactId>javapoet</artifactId>
  <version>1.13.0</version>
</dependency>

or Gradle:

compile 'com.squareup:javapoet:1.13.0'

Snapshots of the development version are available in Sonatype's snapshots repository.

License

Copyright 2015 Square, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

JavaWriter

JavaPoet is the successor to JavaWriter. New projects should prefer JavaPoet because it has a stronger code model: it understands types and can manage imports automatically. JavaPoet is also better suited to composition: rather than streaming the contents of a .java file top-to-bottom in a single pass, a file can be assembled as a tree of declarations.

JavaWriter continues to be available in GitHub and Maven Central.

javapoet (square/javapoet)

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10.8K ·GitHub
Javapoet
archived
这是干什么的?一个用来生成 .java 源文件的 Java API。典型用途是注解处理，以及让生成的代码与元数据（比如数据库表结构或协议格式）保持同步——再也不用手写那些重复的样板代码了。
它是加到项目里用的库，还是单独运行的工具?是一个库，你通过 Maven 或 Gradle 添加，然后在自己的 Java 代码里调用。它把类、方法、字段、参数和注解建模成带构建器的不可变对象——比如 TypeSpec、MethodSpec、FieldSpec 等。
怎么把它加到我的项目里?下载最新的 .jar，或者添加 Maven/Gradle 依赖；开发快照版会发布到 Sonatype 的快照仓库。完整的 API 可以查阅 Javadoc。
这个项目还在维护吗?没有了。Square 已于 2020-10-10 停止维护（弃用）JavaPoet。如果想用最新的 Java 语言特性，README 指向了 Palantir 的 JavaPoet 分支——切换过去意味着更换新的 Maven 坐标、新的导入，还有一些 API 变动。
生成的代码能在 Android 上运行吗?可以——生成的代码能跑在 JVM、Android 和 GWT 上。不过代码生成器本身用到了 javax.lang.model.element.Modifier，这个在 Android 上不可用，所以生成代码这一步要在普通的 JVM 里进行。
生成的文件里的导入（import）需要我自己处理吗?不用。任何类型都可以用 $T 占位符，JavaPoet 会自动生成 import 语句块——包括那些还不存在、通过 ClassName 引用的类。
方法体怎么写——它会构建语法树吗?不会。它只建模声明部分；方法和构造函数的函数体是字符串，采用类似 String.format 的语法：$L 表示字面量，$S 表示会转义的字符串，$T 表示类型，$N 表示其他声明的名称。addStatement()、beginControlFlow() 这类辅助方法会自动处理分号、大括号和缩进。
生成的源代码怎么拿出来?可以写到 System.out，用 JavaFile.toString() 拿到字符串，或者用 JavaFile.writeTo() 直接写入文件系统。
为什么说它是 JavaWriter 的后继者?JavaPoet 的代码模型更强大——它理解类型并自动管理 import——而且它是把文件组装成一棵声明树，而不是从上到下一次性的流式输出，这让代码组合起来更容易。
What are similar projects?butterknife, auto, gson, lombok, Kof4j, gradle, EventBus, ARouter
Which topics is it in?jvm, foss, code-generation, utility, developers, java, android, free, api, tool, apache-2.0, library
Creator
square
Size
1.9 MB
Stars
10.8K
Updated
CommitOct 10
Age
13y
Commits · 90 Days