字符串中占位符替换-mybatis学习笔记

1. 编写TokenHandler实现类（从输入参数中获取value替换sql中的占位符，这里使用Map承载）

   private static class VariableTokenHandler implements TokenHandler {
          
     private Map<String, String> variables = new HashMap<>();
     private VariableTokenHandler(Map<String, String> variables) {
          
         this.variables = variables;
     }
     @Override
     public String handleToken(String content) {
          
         String value = variables.get(content);
         if (StringUtils.isEmpty(value)){
          
             return null ;
         }else {
          
             return "'"+value+"'" ;
         }
     }
   }
   

2. 整理输入参数到Map对象中

   Map<String,String> params = new HashMap<>() ;
   params.put("name","zhangsan") ;
   params.put("age","18") ;
   

3. 编写字符串模板

   String sqlTemplate = "insert into user(username,age,sequence) values(${name},${age},myseq.nextval)" ;
   

4. 根据输入参数和字符串模板替换

   VariableTokenHandler handler = new VariableTokenHandler(params);
   // 替换sql模板中的${xxx}占位符
   GenericTokenParser parser = new GenericTokenParser("${", "}", handler);
   String retContent = parser.parse(sqlTemplate);
   

5. 输出结果

   System.out.println(retContent);
   // 输入结果：
   insert into user(username,age,sequence) values('zhangsan','18',myseq.nextval)