This is the second day of my participation in the November Gwen Challenge. Check out the details: the last Gwen Challenge 2021
Lombok is a controversial plug-in, and there’s no denying its magic. It’s a lot of lazy work, but in addition to reducing the amount of code, when a module uses Lombok, the rest of the code that relies on that module needs to introduce Lombok dependencies. Use it in practice
Introduction to the
Project Lombok is a java library that automatically plugs into your editor and build tools, spicing up your java. Never write another getter or equals method again, with one annotation your class has a fully featured builder, Automate your logging variables, and much more.
Lombok is a Java utility that helps developers eliminate Java verbosity, especially for simple Java objects (POJOs). It does this through annotations. By implementing Lombok in a development environment, developers can save a lot of time building methods like hashCode() and equals() and sorting various accessors and mutators.
The installation
IDEA Install Lombok plug-in
1, Setting → Plugin, search Lombok installation
Lombok is already built into IDEA 2020.3.
2. Import Lombok dependencies
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.1812.</version>
<scope>provided</scope>
</dependency>
Copy the codeEclipse installs the Lombok plug-in
1, the official website to download the jar package: projectlombok.org/download
2. Double-click the lombak.jar package
3. Click Install/Update
4. Click Quit Installer to complete the installation
5. After the installation is complete, check whether there is a lombok.jar package in the Eclipse installation path and whether the following content has been added to the eclipse.ini configuration file: -javaagent:D:\eclipse-jee-2021-03-R-win32-x86_64\eclipse\lombok.jar
Lombok often uses annotations
Lombok annotations document
@NonNull
@Cleanup
@Getter and @Setter
@AllArgsConstructor
@RequiredArgsConstructor
@NoArgsConstructor
@ToString
@EqualsAndHashCode
@Data
@NonNull
When used before an argument to a member method or constructor, a non-null check is automatically generated for the argument, and a null-pointer exception is thrown if the argument is null
import lombok.NonNull;
public class NonNullExample extends Something {
private String name;
public NonNullExample(@NonNull Person person) {
this.name = person.getName(); }}Copy the codeThe equivalent of
import lombok.NonNull;
public class NonNullExample extends Something {
private String name;
public NonNullExample(@NonNull Person person) {
if (person == null) {
throw new NullPointerException("person is marked @NonNull but is null");
}
this.name = person.getName(); }}Copy the code@Cleanup
Used in front of a variable to ensure that the resource it represents is automatically closed, by default calling the close() method of the resource
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); }}}Copy the codeThe equivalent of
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(); }}}}Copy the code@Getter and @Setter
In front of a member variable, the corresponding get and set methods are generated for the member variable. You can also specify access modifiers for the generated methods, which default to public
On a class, you can generate corresponding GET and set methods for all non-static member variables in the class.
import lombok.AccessLevel;
import lombok.Getter;
import lombok.Setter;
public class GetterSetterExample {
@Getter
@Setter
private int age;
@Setter(AccessLevel.PROTECTED)
private String name;
}
Copy the codeThe equivalent of
public class GetterSetterExample {
private int age;
private String name;
public int getAge(a) {
return age;
}
public void setAge(int age) {
this.age = age;
}
protected void setName(String name) {
this.name = name; }}Copy the code@AllArgsConstructor / @NoArgsConstructor
Used on a class that generates a full-parameter constructor and a no-parameter constructor for that class
import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;
@AllArgsConstructor
@NoArgsConstructor
public class User {
private int id;
private String name;
private String password;
}
Copy the codeThe equivalent of
public class User {
private int id;
private String name;
private String password;
public User(a) {}public User(int id, String name, String password) {
this.id = id;
this.name = name;
this.password = password; }}Copy the code@ToString
Used on a class to generate the toString() method
- @toString. Exclude Excludes specified fields
- @toString. Include contains the specified fields
import lombok.ToString;
@ToString
public class User {
@ToString.Exclude
private int id;
private String name;
}
Copy the codeThe equivalent of
public class User {
private int id;
private String name;
public User(a) {}public String toString(a) {
return "User(name=" + this.name + ")"; }}Copy the code@EqualsAndHashCode
Generate equals() and hashCode() methods, as well as canEqual() methods to determine whether an object is an instance of the current class, using only non-static and non-transient member variables of the class
- @ EqualsAndHashCode. Exclude excluding specific fields
- @ EqualsAndHashCode. Include contains the specified field
import lombok.EqualsAndHashCode;
@EqualsAndHashCode
public class User {
private int id;
private String name;
}
Copy the codeThe equivalent of
public class User {
private int id;
private String name;
public User(a) {}public boolean equals(Object o) {
if (o == this) {
return true;
} else if(! (oinstanceof User)) {
return false;
} else {
User other = (User)o;
if(! other.canEqual(this)) {
return false;
} else if (this.id ! = other.id) {return false;
} else {
Object this$name = this.name;
Object other$name = other.name;
if (this$name == null) {
if(other$name ! =null) {
return false; }}else if (!this$name.equals(other$name)) {
return false;
}
return true; }}}protected boolean canEqual(Object other) {
return other instanceof User;
}
public int hashCode(a) {
int PRIME = true;
int result = 1;
int result = result * 59 + this.id;
Object $name = this.name;
result = result * 59 + ($name == null ? 43 : $name.hashCode());
returnresult; }}Copy the code@Data
Contains @getter and @setter, @toString, @equalSandHashCode, @noargsConstructor
import lombok.Data;
@Data
public class User {
private int id;
private String name;
}
Copy the codeThe equivalent of
public class User {
private int id;
private String name;
public User(a) {}public int getId(a) {
return this.id;
}
public String getName(a) {
return this.name;
}
public void setId(int id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public boolean equals(Object o) {
if (o == this) {
return true;
} else if(! (oinstanceof User)) {
return false;
} else {
User other = (User)o;
if(! other.canEqual(this)) {
return false;
} else if (this.getId() ! = other.getId()) {return false;
} else {
Object this$name = this.getName();
Object other$name = other.getName();
if (this$name == null) {
if(other$name ! =null) {
return false; }}else if (!this$name.equals(other$name)) {
return false;
}
return true; }}}protected boolean canEqual(Object other) {
return other instanceof User;
}
public int hashCode(a) {
int PRIME = true;
int result = 1;
int result = result * 59 + this.getId();
Object $name = this.getName();
result = result * 59 + ($name == null ? 43 : $name.hashCode());
return result;
}
public String toString(a) {
return "User(id=" + this.getId() + ", name=" + this.getName() + ")"; }}Copy the code