大家在编写springboot项目的过程中可能会接触到lombok这个插件，这个插件可以在编译时帮我生成很多代码。
1、@Data生成Getter和Setter代码，用于类名注释
2、@Getter 生成字段对应的getXXX方法
3、@Setter生成字段对应的setXXX(xxx yyy)方法
4、@Builder构造器设计模式生成个字段的设置属性方法，该字段一般用于一些类参数可以选，可单选，可多选的环境中
5、@Slf4j使用Slf4j中门面模式，适配底层日志框架，slf4j和底层日志框架协调记录日志
6、@NoArgsConstructor生成类的默认构造函数
7、@AllArgsConstructor生成类所有字段的构造函数，常常和@Builder同时出现
8、@ToString，笔者不常用这个
9、var 兼容ECMA规范，可以编译时自动推断数类型的注解
代码如下
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import lombok.ToString;
import lombok.extern.slf4j.Slf4j;
import lombok.var; @Data
@Getter
@Setter
@Slf4j
@NoArgsConstructor
@AllArgsConstructor
@Builder
@ToString
public class LombokClass {
@Setter
private Integer id; @Setter
@Getter
private String name; public void test()
{
var t ="s";
} }
生成代码：
import org.slf4j.Logger;
import org.slf4j.LoggerFactory; public class LombokClass
{
private static final Logger log;
private Integer id;
private String name; public void test() {
final String t = "s";
} public static LombokClassBuilder builder() {
return new LombokClassBuilder();
} @Override
public boolean equals(final Object o) {
if (o == this) {
return true;
}
if (!(o instanceof LombokClass)) {
return false;
}
final LombokClass other = (LombokClass)o;
if (!other.canEqual(this)) {
return false;
}
final Object this$id = this.getId();
final Object other$id = other.getId();
Label_0065: {
if (this$id == null) {
if (other$id == null) {
break Label_0065;
}
}
else if (this$id.equals(other$id)) {
break Label_0065;
}
return false;
}
final Object this$name = this.getName();
final Object other$name = other.getName();
if (this$name == null) {
if (other$name == null) {
return true;
}
}
else if (this$name.equals(other$name)) {
return true;
}
return false;
} protected boolean canEqual(final Object other) {
return other instanceof LombokClass;
} @Override
public int hashCode() {
final int PRIME = 59;
int result = 1;
final Object $id = this.getId();
result = result * 59 + (($id == null) ? 43 : $id.hashCode());
final Object $name = this.getName();
result = result * 59 + (($name == null) ? 43 : $name.hashCode());
return result;
} public Integer getId() {
return this.id;
} public LombokClass() {
} public LombokClass(final Integer id, final String name) {
this.id = id;
this.name = name;
} @Override
public String toString() {
return "LombokClass(id=" + this.getId() + ", name=" + this.getName() + ")";
} public void setId(final Integer id) {
this.id = id;
} public void setName(final String name) {
this.name = name;
} public String getName() {
return this.name;
} static {
log = LoggerFactory.getLogger((Class)LombokClass.class);
} public static class LombokClassBuilder
{
private Integer id;
private String name; LombokClassBuilder() {
} public LombokClassBuilder id(final Integer id) {
this.id = id;
return this;
} public LombokClassBuilder name(final String name) {
this.name = name;
return this;
} public LombokClass build() {
return new LombokClass(this.id, this.name);
} @Override
public String toString() {
return "LombokClass.LombokClassBuilder(id=" + this.id + ", name=" + this.name + ")";
}
}
}
本文要讲解的重点是@Slf4j相关的使用，使用该注解默认生成代码如下
import org.slf4j.Logger; private static final Logger log = org.slf4j.LoggerFactory.getLogger(当前类名.class);
log有以下几个方法info,trace,debug,error,warn及对应的重载方法。
追踪了一下代码，内部会使用StringBuilder这个线程安全类处理，StringBuilder比String速度比较快，他不会创建多个String对象。
以上几个方法常用格式化代码如下（使用{}作为占位符）：
来自：https://examples.javacodegeeks.com/enterprise-java/slf4j/slf4j-format-string-example/
package com.javacodegeeks.slf4.formatting; import java.lang.invoke.MethodHandles;
import java.text.MessageFormat;
import java.util.Calendar; import org.slf4j.Logger;
import org.slf4j.LoggerFactory; /**
* Substituting Parameters!
*
*/
public class Slf4jSusbstitutionExample
{
private static final Logger LOGGER = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass()); public static void main( String[] args )
{
String user = "john";
String application = "gateway"; // Crafting a message without substitution.
// Not a good idea as the String concatenation and evaluation will happen irrespective of whether
// logging level is permissible or not to be logged.
LOGGER.info("Bad experience for user " + user + " at time " + Calendar.getInstance().getTime()); // Substitution with one formatting anchor and one argument
LOGGER.info("Bad experience for user {}", user); // If you happen to forget to provide a substituting object
LOGGER.info("Bad experience for user {}"); // Substitution with two formatting anchors and two arguments
LOGGER.info("Bad experience for user {} at time {}", user, Calendar.getInstance().getTime()); // Substitution with three formatting anchors and three arguments
LOGGER.info("Bad experience for user {} at time {} while accessing {}", user, Calendar.getInstance().getTime(), application); // Escaping formatting anchor
LOGGER.info("ERROR CODE \\{}; Bad experience for user {} at time {}", user, Calendar.getInstance().getTime()); // Formatting anchor with data inside; no problem
LOGGER.info("ERROR CODE {22}; Bad experience for user {} at time {}", user, Calendar.getInstance().getTime()); // Crafting a message with Java's own MessageFormatter.
// Not a good idea as per SLF4J's documentation.
// 1. SLF4J's implementation is 10 times faster than that of MessageFormat.
// 2. Moreover to make sure that the evaluation happens only if that particular logging
// level is allowed, you need to do a check.
if(LOGGER.isInfoEnabled()) {
String message = MessageFormat.format("Bad experience for user {0} at time {1} while accessing {2}", user, Calendar.getInstance().getTime(), application);
LOGGER.info(message);
}
}
}
输出结果：
2017-04-20 20:25:42 INFO Slf4jSusbstitutionExample - Bad experience for user john at time Thu Apr 20 20:25:42 IST 2017
2017-04-20 20:25:42 INFO Slf4jSusbstitutionExample - Bad experience for user john
2017-04-20 20:25:42 INFO Slf4jSusbstitutionExample - Bad experience for user {}
2017-04-20 20:25:42 INFO Slf4jSusbstitutionExample - Bad experience for user john at time Thu Apr 20 20:25:42 IST 2017
2017-04-20 20:25:42 INFO Slf4jSusbstitutionExample - Bad experience for user john at time Thu Apr 20 20:25:42 IST 2017 while accessing gateway
2017-04-20 20:25:42 INFO Slf4jSusbstitutionExample - ERROR CODE {}; Bad experience for user john at time Thu Apr 20 20:25:42 IST 2017
2017-04-20 20:25:42 INFO Slf4jSusbstitutionExample - ERROR CODE {22}; Bad experience for user john at time Thu Apr 20 20:25:42 IST 2017
2017-04-20 20:25:42 INFO Slf4jSusbstitutionExample - Bad experience for user john at time 4/20/17 8:25 PM while accessing gateway
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