Lombok项目是一个Java库，它会自动插入您的编辑器和构建工具中，从而为您的Java增光添彩。 让代码变得更简洁，但可读性和阅读性会变弱。配置 1、pom.xml文件配置
2、cmd相关org.projectlombok lombok 1.18.22 provided
1).得到lombok在Maven仓库的路径D:javarepoorgprojectlomboklombok1.18.22 2).cmd命令:java -jar D:javarepoorgprojectlomboklombok1.18.22lombok-1.18.22.jar3、编辑器相关
选择eclipse安装路径D:javaeclipse
4、安装后相关1).D:javaeclipse下有lombok.jar，eclipse.ini文件自动增加1行-javaagent:D:javaeclipselombok.jar 2).重启eclipse使用 @NoArgsConstructor，@RequiredArgsConstructor，@AllArgsConstructor
无参构造器、部分参数构造器、全参构造器。Lombok没法实现多种参数构造器的重载。
示例lombok示例代码如下
import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;
import lombok.NonNull;
import lombok.RequiredArgsConstructor;
@AllArgsConstructor
@RequiredArgsConstructor
@NoArgsConstructor
public class TestConstructor {
@NonNull private String name;
private int age;
private int score;
}
不使用lombok示例代码如下
import lombok.NonNull;
public class TestConstructor {
@NonNull
private String name;
private int age;
private int score;
public TestConstructor(@NonNull String name, int age, int score) {
if (name == null)
throw new NullPointerException("name is marked non-null but is null");
this.name = name;
this.age = age;
this.score = score;
}
public TestConstructor(@NonNull String name) {
if (name == null)
throw new NullPointerException("name is marked non-null but is null");
this.name = name;
}
public TestConstructor() {}
}
@Getter/@Setter
@Getter/@Setter注解，此注解在属性上，可以为相应的属性自动生成Getter/Setter方法
示例lombok示例代码如下
import lombok.Getter;
import lombok.Setter;
@Setter
@Getter
public class TestSetterGetter {
private String name;
private int age;
private int score;
@Getter(lazy = true) private final double[] cached = calc();
private double[] calc() {
double[] result = new double[10];
for (int i = 1; i < result.length; i++) {
result[i] = Math.sin(i);
}
return result;
}
}
不使用lombok示例代码如下
import java.util.concurrent.atomic.AtomicReference;
public class TestSetterGetter {
private String name;
private int age;
private int score;
public void setName(String name) {
this.name = name;
}
public void setAge(int age) {
this.age = age;
}
public void setScore(int score) {
this.score = score;
}
public String getName() {
return this.name;
}
public int getAge() {
return this.age;
}
public int getScore() {
return this.score;
}
private final AtomicReference
@ToString
类使用@ToString注解，Lombok会生成一个toString()方法，默认情况下，会输出类名、所有属性（会按照属性定义顺序），用逗号来分割。
示例lombok示例代码如下
import lombok.ToString;
class tmp{
private String info = "父类info";
@Override
public String toString() {
return "tmp [info=" + info + "]";
}
}
@ToString(onlyExplicitlyIncluded=true)
public class TestToString extends tmp{
@ToString.Include(name="test")private String name;
@ToString.Include(rank=1) private int age;
@ToString.Include(rank=2) private int score;
}
不使用lombok示例代码如下
class tmp {
private String info = ";
public String toString() {
return "tmp [info=" + this.info + "]";
}
}
public class TestToString extends tmp {
private String name;
private int age;
private int score;
public String toString() {
return "TestToString(score=" + getScore() + ", age=" + getAge() + ", test=" + getName() + ")";
}
}
@EqualsAndHashCode
默认情况下，会使用所有非静态（non-static）和非瞬态（non-transient）属性来生成equals和hasCode，也能通过exclude注解来排除一些属性。
示例lombok示例代码如下
import lombok.EqualsAndHashCode;
@EqualsAndHashCode
public class TestEqualsAndHashCode {
private String name;
private int age;
private int score;
}
不使用lombok示例代码如下
public class TestEqualsAndHashCode {
private String name;
private int age;
private int score;
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof TestEqualsAndHashCode))
return false;
TestEqualsAndHashCode other = (TestEqualsAndHashCode)o;
if (!other.canEqual(this))
return false;
if (this.age != other.age)
return false;
if (this.score != other.score)
return false;
Object this$name = this.name, other$name = other.name;
return !((this$name == null) ? (other$name != null) : !this$name.equals(other$name));
}
protected boolean canEqual(Object other) {
return other instanceof TestEqualsAndHashCode;
}
public int hashCode() {
int PRIME = 59;
result = 1;
result = result * 59 + this.age;
result = result * 59 + this.score;
Object $name = this.name;
return result * 59 + (($name == null) ? 43 : $name.hashCode());
}
}
@Data
整合包，只要加了 @Data 这个注解，等于同时加了以下注解
- @Getter/@Setter
- @ToString
- @EqualsAndHashCode
- @RequiredArgsConstructor
如为final属性，则不会为该属性生成setter方法。
示例lombok示例代码如下
import lombok.Data;
import lombok.NonNull;
@Data
public class TestData {
@NonNull private String name;
private int age;
private int score;
private final String test = "test";
}
不使用lombok示例代码如下
import lombok.NonNull;
public class TestData {
@NonNull
private String name;
private int age;
private int score;
private final String test = "test";
public TestData(@NonNull String name) {
if (name == null)
throw new NullPointerException("name is marked non-null but is null");
this.name = name;
}
public String toString() {
return "TestData(name=" + getName() + ", age=" + getAge() + ", score=" + getScore() + ", test=" + getTest() + ")";
}
public int hashCode() {
int PRIME = 59;
result = 1;
result = result * 59 + getAge();
result = result * 59 + getScore();
Object $name = getName();
result = result * 59 + (($name == null) ? 43 : $name.hashCode());
Object $test = getTest();
return result * 59 + (($test == null) ? 43 : $test.hashCode());
}
protected boolean canEqual(Object other) {
return other instanceof TestData;
}
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof TestData))
return false;
TestData other = (TestData)o;
if (!other.canEqual(this))
return false;
if (getAge() != other.getAge())
return false;
if (getScore() != other.getScore())
return false;
Object this$name = getName(), other$name = other.getName();
if ((this$name == null) ? (other$name != null) : !this$name.equals(other$name))
return false;
Object this$test = getTest(), other$test = other.getTest();
return !((this$test == null) ? (other$test != null) : !this$test.equals(other$test));
}
public void setScore(int score) {
this.score = score;
}
public void setAge(int age) {
this.age = age;
}
public void setName(@NonNull String name) {
if (name == null)
throw new NullPointerException("name is marked non-null but is null");
this.name = name;
}
public String getTest() {
return "test";
}
public int getScore() {
return this.score;
}
public int getAge() {
return this.age;
}
@NonNull
public String getName() {
return this.name;
}
}
@NonNull
该注解用在属性或构造器上，Lombok会生成一个非空的声明，可用于校验参数，能帮助避免空指针。
示例lombok示例代码如下
import lombok.NonNull;
import lombok.RequiredArgsConstructor;
@RequiredArgsConstructor
public class TestNonNull {
@NonNull private String name;
private int age;
private int score;
public String test(@NonNull String teacher) {
return "name:" + name + "n" + "teacher:" + teacher;
}
}
不使用lombok示例代码如下
import lombok.NonNull;
public class TestNonNull {
@NonNull
private String name;
private int age;
private int score;
public TestNonNull(@NonNull String name) {
if (name == null)
throw new NullPointerException("name is marked non-null but is null");
this.name = name;
}
public String test(@NonNull String teacher) {
if (teacher == null)
throw new NullPointerException("teacher is marked non-null but is null");
return "name:" + this.name + "n" + "teacher:" + teacher;
}
}
@Cleanup
该注解能帮助我们自动调用close()方法，很大的简化了代码。
示例lombok示例代码如下
import lombok.Cleanup;
public class TestCleanup {
public int noParamSqlUpdate(String noParamSql) throws Exception {
@Cleanup Connection con = getConnection();
//发送sql语句
@Cleanup PreparedStatement ps = con.prepareStatement(noParamSql);
int count = ps.executeUpdate();
//关闭连接
//@Cleanup完成
return count;
}
}
不使用lombok示例代码如下
public class TestCleanup {
public int noParamSqlUpdate(String noParamSql) throws Exception {
Connection con = getConnection();
try {
Exception exception;
PreparedStatement ps = con.prepareStatement(noParamSql);
try {
int count = ps.executeUpdate();
int i = count;
if (Collections.singletonList(ps).get(0) != null)
ps.close();
return i;
} finally {}
if (Collections.singletonList(ps).get(0) != null)
ps.close();
throw exception;
} finally {
if (Collections.singletonList(con).get(0) != null)
con.close();
}
}
}
@Synchronized
@Synchronized是synchronized方法修饰符的更安全的变体。与一样synchronized，注释只能在静态方法和实例方法上使用。它的操作类似于synchronized关键字，但是它锁定在不同的对象上。关键字锁定在上this，但注解锁定在名为$ lock的字段上，该字段是私有的。
示例lombok示例代码如下
import lombok.Synchronized;
public class TestSynchronized {
//从连接池借连接
@Synchronized
private static Connection getConnection() throws Exception {
return pool.getConnection();
}
}
不使用lombok示例代码如下
public class TestSynchronized {
private static final Object $LOCK = new Object[0];
private static Connection getConnection() throws Exception {
synchronized ($LOCK) {
return pool.getConnection();
}
}
}
@Value
整合包，但是他会把所有的变量都设成 final 的，其他的就跟 @Data 一样，等于同时加了以下注解
- @Getter (注意没有setter)
- @ToString
- @EqualsAndHashCode
- @AllArgsConstructor
lombok示例代码如下
import lombok.Value;
@Value
public class TestValue {
private String name;
private int age;
private int score;
}
不使用lombok示例代码如下
public final class TestValue {
private final String name;
private final int age;
private final int score;
public TestValue(String name, int age, int score) {
this.name = name;
this.age = age;
this.score = score;
}
public String toString() {
return "TestValue(name=" + getName() + ", age=" + getAge() + ", score=" + getScore() + ")";
}
public int hashCode() {
int PRIME = 59;
result = 1;
result = result * 59 + getAge();
result = result * 59 + getScore();
Object $name = getName();
return result * 59 + (($name == null) ? 43 : $name.hashCode());
}
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof TestValue))
return false;
TestValue other = (TestValue)o;
if (getAge() != other.getAge())
return false;
if (getScore() != other.getScore())
return false;
Object this$name = getName(), other$name = other.getName();
return !((this$name == null) ? (other$name != null) : !this$name.equals(other$name));
}
public int getScore() {
return this.score;
}
public int getAge() {
return this.age;
}
public String getName() {
return this.name;
}
}
@SneakyThrows
@SneakyThrows用的并不多，因为只是将异常抛出throw，还是需要你在调用方法时对异常做处理。它只是一个try-catch的简单写法。
示例lombok示例代码如下
import lombok.SneakyThrows;
public class TestSneakyThrows {
@SneakyThrows(Exception.class)
public void calc() {
int a = 1;
System.out.println(a/0);
}
}
不使用lombok示例代码如下
public class TestSneakyThrows {
public void calc() {
try {
int a = 1;
System.out.println(a / 0);
} catch (Exception $ex) {
throw $ex;
}
}
}
@With
作用于类，生成多个 with + 变量名的方法（个数为所有成员变量，不包含 @NonNull），作用于变量，生成 with + 变量名的方法，返回当前对象，需要提供全参（不包含静态变量）构造方法
示例lombok示例代码如下
import lombok.AllArgsConstructor;
import lombok.With;
@With
@AllArgsConstructor
public class TestWith {
@With private String name;
private int age;
private int score;
}
不使用lombok示例代码如下
public class TestWith {
private String name;
private int age;
private int score;
public TestWith withAge(int age) {
return (this.age == age) ? this : new TestWith(this.name, age, this.score);
}
public TestWith withScore(int score) {
return (this.score == score) ? this : new TestWith(this.name, this.age, score);
}
public TestWith(String name, int age, int score) {
this.name = name;
this.age = age;
this.score = score;
}
public TestWith withName(String name) {
return (this.name == name) ? this : new TestWith(name, this.age, this.score);
}
}
@Builder
@Builder注解 可以很方便的使用构造模式
示例lombok示例代码如下
import lombok.Builder;
@Builder
public class TestBuilder {
private String name;
private int age;
private int score;
public static void main(String[] args) {
TestBuilderBuilder testBuilderBuilder = TestBuilder.builder();
testBuilderBuilder.name("zhangsan");
testBuilderBuilder.age(20);
testBuilderBuilder.score(100);
TestBuilder testBuilder = testBuilderBuilder.build();
}
}
不使用lombok示例代码如下
public class TestBuilder {
private String name;
private int age;
private int score;
public static TestBuilderBuilder builder() {
return new TestBuilderBuilder();
}
TestBuilder(String name, int age, int score) {
this.name = name;
this.age = age;
this.score = score;
}
public static class TestBuilderBuilder {
private String name;
private int age;
private int score;
public TestBuilderBuilder name(String name) {
this.name = name;
return this;
}
public TestBuilderBuilder age(int age) {
this.age = age;
return this;
}
public TestBuilderBuilder score(int score) {
this.score = score;
return this;
}
public TestBuilder build() {
return new TestBuilder(this.name, this.age, this.score);
}
public String toString() {
return "TestBuilder.TestBuilderBuilder(name=" + this.name + ", age=" + this.age + ", score=" + this.score + ")";
}
}
public static void main(String[] args) {
TestBuilderBuilder testBuilderBuilder = builder();
testBuilderBuilder.name("zhangsan");
testBuilderBuilder.age(20);
testBuilderBuilder.score(100);
TestBuilder testBuilder = testBuilderBuilder.build();
}
}
turn this;
}
public TestBuilderBuilder age(int age) {
this.age = age;
return this;
}
public TestBuilderBuilder score(int score) {
this.score = score;
return this;
}
public TestBuilder build() {
return new TestBuilder(this.name, this.age, this.score);
}
public String toString() {
return "TestBuilder.TestBuilderBuilder(name=" + this.name + ", age=" + this.age + ", score=" + this.score + ")";
}
}
public static void main(String[] args) {
TestBuilderBuilder testBuilderBuilder = builder();
testBuilderBuilder.name("zhangsan");
testBuilderBuilder.age(20);
testBuilderBuilder.score(100);
TestBuilder testBuilder = testBuilderBuilder.build();
}
}
