lombok插件/slf4j中字符串格式化

大家在編寫springboot項目的過程中可能會接觸到lombok這個插件，這個插件可以在編譯時幫我生成很多代碼。

1、@Data生成Getter和Setter代碼，用於類名注釋

2、@Getter 生成字段對應的getXXX方法

3、@Setter生成字段對應的setXXX(xxx yyy)方法

4、@Builder構造器設計模式生成個字段的設置屬性方法，該字段一般用於一些類參數可以選，可單選，可多選的環境中

5、@Slf4j使用Slf4j中門面模式，適配底層日志框架，slf4j和底層日志框架協調記錄日志

6、@NoArgsConstructor生成類的默認構造函數

7、@AllArgsConstructor生成類所有字段的構造函數，常常和@Builder同時出現

8、@ToString，筆者不常用這個

9、var 兼容ECMA規范，可以編譯時自動推斷數類型的注解

代碼如下

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";
    }


}

 生成代碼：

 

 

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 + ")";
        }
    }
}

 

 

本文要講解的重點是@Slf4j相關的使用，使用該注解默認生成代碼如下

import org.slf4j.Logger;


private static final Logger log = org.slf4j.LoggerFactory.getLogger(當前類名.class);

log有以下幾個方法info,trace,debug,error,warn及對應的重載方法。

追蹤了一下代碼，內部會使用StringBuilder這個線程安全類處理，StringBuilder比String速度比較快，他不會創建多個String對象。

 

 

 以上幾個方法常用格式化代碼如下（使用{}作為占位符）：

來自：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);
        }
    }
}

輸出結果：

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

 

本博客lombok其他文章:

idea中Lombok的Buider構造器模式，getter/setter正確使用方法

 lombok編譯時注解@Slf4j的使用及相關依賴包

Lombok子類與父類的@Builder注解沖突