取出一个实体中不为null的属性和属性值

冷不防 2022-03-07 08:24 424阅读 0赞

多条件复杂查询，不知具体有多少个条件，一个一个判断代码冗长，只想取出有值的条件，拼接到sql上，比如有个User类，有属性name,id， 当只有id有值时，返回"and id =xxxx"

用法，将自己的bean对象继承ParameterBaseUtils，用this.gainConditionFromObjectByField()即可

package cn.com.suntree.cmp.utils;
    
    import java.lang.reflect.Field;
    import java.lang.reflect.Method;
    
    public class ParameterBaseUtils {
    
        /**
         * 返回有的值条件,比如有个User类，有属性name,id
         * 当只有id有值时，返回and id ={id的值}
         *
         * @return
         * @throws
         * @author ld
         * @date 2019/02/11 14:13
         */
        public String gainConditionFromObjectByField() {
    
            StringBuffer sb = new StringBuffer();
            Field[] fields = this.getClass().getDeclaredFields();//取出所有属性
            for (int i = 0; i < fields.length; i++) {
                Field f = fields[i];
                String fieldName = f.getName();
                Object value = getFieldValue(this, fieldName);//取属性值
                if (CommonUtil.check(value)) {
                    Class<?> type = f.getType();
                    if ("class java.lang.String".equals(type.toString())) {
                        sb.append(" and " + fieldName + "='" + value + "'");
                    } else {
                        sb.append(" and " + fieldName + "=" + value);
                    }
                }
                continue;
            }
            return sb.toString();
        }
    
    
        private String getFieldValue(Object owner, String fieldName) {
            Object o = invokeMethod(owner, fieldName, null);
            if (CommonUtil.check(o)) {
                return o.toString();
            }
            return null;
        }
    
    
        /**
         * 执行某个Field的getField方法
         *
         * @param owner     类
         * @param fieldName 类的属性名称
         * @param args      参数，默认为null
         * @return
         */
        private Object invokeMethod(Object owner, String fieldName, Object[] args) {
            Class<? extends Object> ownerClass = owner.getClass();
    
            //fieldName -> FieldName
            String methodName = fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);
    
            Method method = null;
            try {
                method = ownerClass.getMethod("get" + methodName);
            } catch (SecurityException e) {
    
                //e.printStackTrace();
            } catch (NoSuchMethodException e) {
                // e.printStackTrace();
                return "";
            }
    
            //invoke getMethod
            try {
                return method.invoke(owner);
            } catch (Exception e) {
                return "";
            }
        }
    }