lombok:推荐使用的编译时Getter/Setter等类似代码生成库

dance 发布于2019-08-14 15:42 / 3413人阅读

摘要：每个用的孩子都应该了解下主要依赖编译时代码生成技术，帮你自动生成基于模板的常用的代码，譬如最常见的与。另一种是通过类似于这样基于注解的在运行时利用反射动态添加，不过这样的缺陷是会影响性能，并且有一定局限性。

Lombok

每个用Java的孩子都应该了解下Lombok

Lombok主要依赖编译时代码生成技术，帮你自动生成基于模板的常用的Java代码，譬如最常见的Getter与Setter。之前动态的插入Getter与Setter主要有两种，一个是像Intellij与Eclipse这样在开发时动态插入，缺点是这样虽然不用你手动写，但是还是会让你的代码异常的冗长。另一种是通过类似于Spring这样基于注解的在运行时利用反射动态添加，不过这样的缺陷是会影响性能，并且有一定局限性。

文章的Github Repo
部分测试代码参考这里

Quick Start Installation

笔者目前用的开发环境是Intellij+Gradle，这里只介绍下这种搭建方式，其他的基于Eclipse或者Maven的可以到官网主页查看。

（1）在Intellij中添加Plugin

Go to File > Settings > Plugins

Click on Browse repositories...

Search for Lombok Plugin

Click on Install plugin

Restart Android Studio

（2）允许注解处理

Settings -> Compiler -> Annotation Processors

（3）Gradle中添加依赖

compile "org.projectlombok:lombok:1.12.6"

动态类型推导 Data Model:数据模型 Getter&Setter

源代码：

import lombok.AccessLevel;

import lombok.Getter;

import lombok.Setter;



public class GetterSetterExample {

    /**

     * Age of the person. Water is wet.

     * 

     * @param age New value for this person"s age. Sky is blue.

     * @return The current value of this person"s age. Circles are round.

     */

    @Getter @Setter private int age = 10;

    

    /**

     * Name of the person.

     * -- SETTER --

     * Changes the name of this person.

     * 

     * @param name The new value.

     */

    @Setter(AccessLevel.PROTECTED) private String name;

    

    @Override public String toString() {

        return String.format("%s (age: %d)", name, age);

    }

}

编译之后的代码：



public class GetterSetterExample {

    /**

     * Age of the person. Water is wet.

     */

    private int age = 10;



    /**

     * Name of the person.

     */

    private String name;

    

    @Override public String toString() {

        return String.format("%s (age: %d)", name, age);

    }

    

    /**

     * Age of the person. Water is wet.

     *

     * @return The current value of this person"s age. Circles are round.

     */

    public int getAge() {

        return age;

    }

    

    /**

     * Age of the person. Water is wet.

     *

     * @param age New value for this person"s age. Sky is blue.

     */

    public void setAge(int age) {

        this.age = age;

    }

    

    /**

     * Changes the name of this person.

     *

     * @param name The new value.

     */

    protected void setName(String name) {

        this.name = name;

    }

}

Lazy Getter

源代码：

import lombok.Getter;



public class GetterLazyExample {

    @Getter(lazy=true) private final double[] cached = expensive();

    

    private double[] expensive() {

        double[] result = new double[1000000];

        for (int i = 0; i < result.length; i++) {

            result[i] = Math.asin(i);

        }

        return result;

    }

}

编译之后：

public class GetterSetterExample {

    /**

     * Age of the person. Water is wet.

     */

    private int age = 10;



    /**

     * Name of the person.

     */

    private String name;

    

    @Override public String toString() {

        return String.format("%s (age: %d)", name, age);

    }

    

    /**

     * Age of the person. Water is wet.

     *

     * @return The current value of this person"s age. Circles are round.

     */

    public int getAge() {

        return age;

    }

    

    /**

     * Age of the person. Water is wet.

     *

     * @param age New value for this person"s age. Sky is blue.

     */

    public void setAge(int age) {

        this.age = age;

    }

    

    /**

     * Changes the name of this person.

     *

     * @param name The new value.

     */

    protected void setName(String name) {

        this.name = name;

    }

}

Data

源代码:

import lombok.AccessLevel;

import lombok.Setter;

import lombok.Data;

import lombok.ToString;



@Data public class DataExample {

    private final String name;

    @Setter(AccessLevel.PACKAGE) private int age;

    private double score;

    private String[] tags;

    

    @ToString(includeFieldNames=true)

    @Data(staticConstructor="of")

    public static class Exercise {

        private final String name;

        private final T value;

    }

}

编译后：

import java.util.Arrays;



public class DataExample {

    private final String name;

    private int age;

    private double score;

    private String[] tags;

    

    public DataExample(String name) {

        this.name = name;

    }

    

    public String getName() {

        return this.name;

    }

    

    void setAge(int age) {

        this.age = age;

    }

    

    public int getAge() {

        return this.age;

    }

    

    public void setScore(double score) {

        this.score = score;

    }

    

    public double getScore() {

        return this.score;

    }

    

    public String[] getTags() {

        return this.tags;

    }

    

    public void setTags(String[] tags) {

        this.tags = tags;

    }

    

    @Override public String toString() {

        return "DataExample(" + this.getName() + ", " + this.getAge() + ", " + this.getScore() + ", " + Arrays.deepToString(this.getTags()) + ")";

    }

    

    protected boolean canEqual(Object other) {

        return other instanceof DataExample;

    }

    

    @Override public boolean equals(Object o) {

        if (o == this) return true;

        if (!(o instanceof DataExample)) return false;

        DataExample other = (DataExample) o;

        if (!other.canEqual((Object)this)) return false;

        if (this.getName() == null ? other.getName() != null : !this.getName().equals(other.getName())) return false;

        if (this.getAge() != other.getAge()) return false;

        if (Double.compare(this.getScore(), other.getScore()) != 0) return false;

        if (!Arrays.deepEquals(this.getTags(), other.getTags())) return false;

        return true;

    }

    

    @Override public int hashCode() {

        final int PRIME = 59;

        int result = 1;

        final long temp1 = Double.doubleToLongBits(this.getScore());

        result = (result*PRIME) + (this.getName() == null ? 43 : this.getName().hashCode());

        result = (result*PRIME) + this.getAge();

        result = (result*PRIME) + (int)(temp1 ^ (temp1 >>> 32));

        result = (result*PRIME) + Arrays.deepHashCode(this.getTags());

        return result;

    }

    

    public static class Exercise {

        private final String name;

        private final T value;

        

        private Exercise(String name, T value) {

            this.name = name;

            this.value = value;

        }

        

        public static  Exercise of(String name, T value) {

            return new Exercise(name, value);

        }

        

        public String getName() {

            return this.name;

        }

        

        public T getValue() {

            return this.value;

        }

        

        @Override public String toString() {

            return "Exercise(name=" + this.getName() + ", value=" + this.getValue() + ")";

        }

        

        protected boolean canEqual(Object other) {

            return other instanceof Exercise;

        }

        

        @Override public boolean equals(Object o) {

            if (o == this) return true;

            if (!(o instanceof Exercise)) return false;

            Exercise other = (Exercise) o;

            if (!other.canEqual((Object)this)) return false;

            if (this.getName() == null ? other.getValue() != null : !this.getName().equals(other.getName())) return false;

            if (this.getValue() == null ? other.getValue() != null : !this.getValue().equals(other.getValue())) return false;

            return true;

        }

        

        @Override public int hashCode() {

            final int PRIME = 59;

            int result = 1;

            result = (result*PRIME) + (this.getName() == null ? 43 : this.getName().hashCode());

            result = (result*PRIME) + (this.getValue() == null ? 43 : this.getValue().hashCode());

            return result;

        }

    }

}

Object Constructor

源代码

import lombok.AccessLevel;

import lombok.RequiredArgsConstructor;

import lombok.AllArgsConstructor;

import lombok.NonNull;



@RequiredArgsConstructor(staticName = "of")

@AllArgsConstructor(access = AccessLevel.PROTECTED)

public class ConstructorExample {

    private int x, y;

    @NonNull private T description;

    

    @NoArgsConstructor

    public static class NoArgsExample {

        @NonNull private String field;

    }

}

编译之后：

public class ConstructorExample {

    private int x, y;

    @NonNull private T description;

    

    private ConstructorExample(T description) {

        if (description == null) throw new NullPointerException("description");

        this.description = description;

    }

    

    public static  ConstructorExample of(T description) {

        return new ConstructorExample(description);

    }

    

    @java.beans.ConstructorProperties({"x", "y", "description"})

    protected ConstructorExample(int x, int y, T description) {

        if (description == null) throw new NullPointerException("description");

        this.x = x;

        this.y = y;

        this.description = description;

    }

    

    public static class NoArgsExample {

        @NonNull private String field;

        

        public NoArgsExample() {

        }

    }

}

Builder

源代码：

package wx.toolkits.basic.class_object.utils.lombok.object;

import lombok.experimental.Builder;

import java.util.Set;

@Builder
public class BuilderExample {
    private String name;
    private int age;
    private Set occupations;

    public static void main(String args[]) {

        BuilderExample builderExample = BuilderExample.builder().build();

    }

}

编译之后的源代码：

import java.util.Set;



public class BuilderExample {

    private String name;

    private int age;

    private Set occupations;

    

    BuilderExample(String name, int age, Set occupations) {

        this.name = name;

        this.age = age;

        this.occupations = occupations;

}

    

    public static BuilderExampleBuilder builder() {

        return new BuilderExampleBuilder();

    }

    

    public static class BuilderExampleBuilder {

        private String name;

        private int age;

        private java.util.ArrayList occupations;

        

        BuilderExampleBuilder() {

        }

        

        public BuilderExampleBuilder name(String name) {

            this.name = name;

            return this;

        }

        

        public BuilderExampleBuilder age(int age) {

            this.age = age;

            return this;

        }

        

        public BuilderExampleBuilder occupation(String occupation) {

            if (this.occupations == null) {

                this.occupations = new java.util.ArrayList();

            }

            

            this.occupations.add(occupation);

            return this;

        }

        

        public BuilderExampleBuilder occupations(Collection occupations) {

            if (this.occupations == null) {

                this.occupations = new java.util.ArrayList();

            }



            this.occupations.addAll(occupations);

            return this;

        }

        

        public BuilderExampleBuilder clearOccupations() {

            if (this.occupations != null) {

                this.occupations.clear();

            }

            

            return this;

        }



        public BuilderExample build() {

            // complicated switch statement to produce a compact properly sized immutable set omitted.

            // go to https://projectlombok.org/features/Singular-snippet.html to see it.

            Set occupations = ...;

            return new BuilderExample(name, age, occupations);

        }

        

        @java.lang.Override

        public String toString() {

            return "BuilderExample.BuilderExampleBuilder(name = " + this.name + ", age = " + this.age + ", occupations = " + this.occupations + ")";

        }

    }

}

Exception:异常处理 NonNull

源代码：

import lombok.NonNull;



public class NonNullExample extends Something {

    private String name;

    

    public NonNullExample(@NonNull Person person) {

        super("Hello");

        this.name = person.getName();

    }

}

编译之后：

import lombok.NonNull;



public class NonNullExample extends Something {

    private String name;

    

    public NonNullExample(@NonNull Person person) {

        super("Hello");

        if (person == null) {

            throw new NullPointerException("person");

        }

        this.name = person.getName();

    }

}

SneakyThrows

源代码：

import lombok.SneakyThrows;



public class SneakyThrowsExample implements Runnable {

    @SneakyThrows(UnsupportedEncodingException.class)

    public String utf8ToString(byte[] bytes) {

        return new String(bytes, "UTF-8");

    }

    

    @SneakyThrows

    public void run() {

        throw new Throwable();

    }

}

编译之后：

import lombok.Lombok;



public class SneakyThrowsExample implements Runnable {

    public String utf8ToString(byte[] bytes) {

        try {

            return new String(bytes, "UTF-8");

        } catch (UnsupportedEncodingException e) {

            throw Lombok.sneakyThrow(e);

        }

    }

    

    public void run() {

        try {

            throw new Throwable();

        } catch (Throwable t) {

            throw Lombok.sneakyThrow(t);

        }

    }

}

Thread:线程 Synchronized

源代码：

import lombok.Synchronized;



public class SynchronizedExample {

    private final Object readLock = new Object();

    

    @Synchronized

    public static void hello() {

        System.out.println("world");

    }

    

    @Synchronized

    public int answerToLife() {

        return 42;

    }

    

    @Synchronized("readLock")

    public void foo() {

        System.out.println("bar");

    }

}

编译之后：

public class SynchronizedExample {

    private static final Object $LOCK = new Object[0];

    private final Object $lock = new Object[0];

    private final Object readLock = new Object();

    

    public static void hello() {

        synchronized($LOCK) {

            System.out.println("world");

        }

    }

    

    public int answerToLife() {

        synchronized($lock) {

            return 42;

        }

    }

    

    public void foo() {

        synchronized(readLock) {

            System.out.println("bar");

        }

    }

}

Utils Cleanup

源代码：

import lombok.Cleanup;

import java.io.*;



public class CleanupExample {

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

        @Cleanup InputStream in = new FileInputStream(args[0]);

        @Cleanup OutputStream out = new FileOutputStream(args[1]);

        byte[] b = new byte[10000];

        while (true) {

            int r = in.read(b);

            if (r == -1) break;

            out.write(b, 0, r);

        }

    }

}

编译之后：

import java.io.*;



public class CleanupExample {

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

        InputStream in = new FileInputStream(args[0]);

        try {

            OutputStream out = new FileOutputStream(args[1]);

            try {

                byte[] b = new byte[10000];

                while (true) {

                    int r = in.read(b);

                    if (r == -1) break;

                    out.write(b, 0, r);

                }

            } finally {

                if (out != null) {

                    out.close();

                }

            }

        } finally {

            if (in != null) {

                in.close();

            }

        }

    }

}

Log:日志

使用@Log或者类似注解可以为类自动创建一个log对象，其效果如下所示：

@CommonsLog

Creates private static final org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory.getLog(LogExample.class);

@Log

Creates private static final java.util.logging.Logger log = java.util.logging.Logger.getLogger(LogExample.class.getName());

@Log4j

Creates private static final org.apache.log4j.Logger log = org.apache.log4j.Logger.getLogger(LogExample.class);

@Log4j2

Creates private static final org.apache.logging.log4j.Logger log = org.apache.logging.log4j.LogManager.getLogger(LogExample.class);

@Slf4j

Creates private static final org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(LogExample.class);

@XSlf4j

Creates private static final org.slf4j.ext.XLogger log = org.slf4j.ext.XLoggerFactory.getXLogger(LogExample.class);

使用了Lombok之后的代码如下：

import lombok.extern.java.Log;

import lombok.extern.slf4j.Slf4j;



@Log

public class LogExample {

    

    public static void main(String... args) {

        log.error("Something"s wrong here");

    }

}



@Slf4j

public class LogExampleOther {

    

    public static void main(String... args) {

        log.error("Something else is wrong here");

    }

}



@CommonsLog(topic="CounterLog")

public class LogExampleCategory {



    public static void main(String... args) {

        log.error("Calling the "CounterLog" with a message");

    }

}

编译之后的代码如下：

public class LogExample {

    private static final java.util.logging.Logger log = java.util.logging.Logger.getLogger(LogExample.class.getName());

    

    public static void main(String... args) {

        log.error("Something"s wrong here");

    }

}



public class LogExampleOther {

    private static final org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(LogExampleOther.class);

    

    public static void main(String... args) {

        log.error("Something else is wrong here");

    }

}



public class LogExampleCategory {

    private static final org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory.getLog("CounterLog");



    public static void main(String... args) {

        log.error("Calling the "CounterLog" with a message");

    }

}

其他可配置的参数为：

lombok.log.fieldName = an identifier (default: log)

The generated logger fieldname is by default "log", but you can change it to a different name with this setting.

lombok.log.fieldIsStatic = [true | false] (default: true)

Normally the generated logger is a static field. By setting this key to false, the generated field will be an instance field instead.

lombok.log.flagUsage = [warning | error] (default: not set)

Lombok will flag any usage of any of the various log annotations as a warning or error if configured.

lombok.log.apacheCommons.flagUsage = [warning | error] (default: not set)

Lombok will flag any usage of @lombok.extern.apachecommons.CommonsLog as a warning or error if configured.

lombok.log.javaUtilLogging.flagUsage = [warning | error] (default: not set)

Lombok will flag any usage of @lombok.extern.java.Log as a warning or error if configured.

lombok.log.log4j.flagUsage = [warning | error] (default: not set)

Lombok will flag any usage of @lombok.extern.log4j.Log4j as a warning or error if configured.

lombok.log.log4j2.flagUsage = [warning | error] (default: not set)

Lombok will flag any usage of @lombok.extern.log4j.Log4j2 as a warning or error if configured.

lombok.log.slf4j.flagUsage = [warning | error] (default: not set)

Lombok will flag any usage of @lombok.extern.slf4j.Slf4j as a warning or error if configured.

lombok.log.xslf4j.flagUsage = [warning | error] (default: not set)

Lombok will flag any usage of @lombok.extern.slf4j.XSlf4j as a warning or error if configured.

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