java：${}的模板字符串替换

1 前言

模板字符串中经常使用${变量名}来进行字符串的变量替换，可使用commons-text库中的工具方式实现该功能。

依赖配置如下：

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.5.4</version>
</parent>

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        
		<dependency>
			<groupId>org.apache.commons</groupId>
			<artifactId>commons-text</artifactId>
			<version>1.9</version>
		</dependency>
		
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-collections4</artifactId>
            <version>4.4</version>
        </dependency>
			
		<dependency>
		    <groupId>org.projectlombok</groupId>
		    <artifactId>lombok</artifactId>
		    <version>1.18.22</version>
		</dependency>
</dependencies>

2 使用

package com.xiaoxu.tool.demo;

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.collections4.MapUtils;
import org.apache.commons.text.StringSubstitutor;
import org.springframework.util.StringUtils;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

/**
 * @author xiaoxu
 * @date 2022-08-08
 * spring_boot:com.xiaoxu.tool.demo.TestReplace
 */
@Slf4j
public class TestReplace {

    private static final String prefix = "${";
    private static final String suffix = "}";
    /*
    * commons-text
    * */
    public static String replaceVar(Map<String,String> vars,String template){
        if(!StringUtils.hasLength(template)){
            log.info(String.format("调用%s方法失败,模板字符串替换失败,模板字符串不能为空",
                    Thread.currentThread().getStackTrace()[1].getMethodName()));
            return null;
        }
        if(MapUtils.isEmpty(vars)){
            log.info(String.format("调用%s方法失败,模板字符串替换失败,map不能为空",
                    Thread.currentThread().getStackTrace()[1].getMethodName()));
            return null;
        }
        List<String> tempStrs = vars.keySet().stream().map(s -> prefix + s + suffix).
                collect(Collectors.toList());
        tempStrs.forEach(t->{
            if(!template.contains(t)){
                throw new RuntimeException(String.format("调用%s方法失败,模板字符串替换失败,map的key必须存在于模板字符串中",
                        Thread.currentThread().getStackTrace()[1].getMethodName()));
            }
        });
        StringSubstitutor stringSubstitutor = new StringSubstitutor(vars);
        return stringSubstitutor.replace(template);
    }

    public static void main(String[] args) {
        /*
         * 错误的场景：比如${变量}，{}内不能含有空格等等
         * System.out.println(replaceVar(vals, "我叫${ name},今年${age }岁."));
         * System.out.println(replaceVar(new HashMap<>(), temp));
         * System.out.println(replaceVar(vals, "我叫xiaoxu"));
         * System.out.println(replaceVar(vals, "我叫${name},今年${age1}岁."));
         * */
        Map<String,String> vals = new HashMap<>();
        vals.put("name","xiaoxu");
        vals.put("age","36");
        String temp = "我叫${name},今年${age}岁.";
        System.out.println(replaceVar(vals, temp));
    }
}

执行结果：

我叫xiaoxu,今年36岁.