Java Poet

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.

Hello World

  • Import jar
<dependency>
    <groupId>com.squareup</groupId>
    <artifactId>javapoet</artifactId>
    <version>1.9.0</version>
</dependency>
  • HelloWorld.java
package com.ryo.generator.java;

import com.squareup.javapoet.JavaFile;
import com.squareup.javapoet.MethodSpec;
import com.squareup.javapoet.TypeSpec;

import javax.lang.model.element.Modifier;
import java.io.IOException;

/**
 * Java poet demo
 * Created by bbhou on 2017/9/29.
 */
public class HelloWorld {

    public static void main(String[] args) throws IOException {
        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);
    }
}

result:

package com.example.helloworld;

import java.lang.String;
import java.lang.System;

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