java-classic-code/springjdbc-sql-template/DOResultTransformer.java

package com.primeton.filetransfer.server.template;


import lombok.Getter;
import lombok.NonNull;
import lombok.Setter;
import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.persistence.Column;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 *
 * JDBC ResultSet 转 Entity Object 快捷方法
 *
 * <pre>
 *
 * Created by zhaopx.
 * User: zhaopx
 * Date: 2022/3/1
 * Time: 下午6:35
 * Vendor: primeton.com
 *
 * </pre>
 *
 * @author zhaopx
 */
public class DOResultTransformer<T> implements ResultTransformer<T> {

    /**
     *
     */
    private static final long serialVersionUID = 1L;
    private static Logger logger = LoggerFactory.getLogger(DOResultTransformer.class);

    /**
     * 驼峰转下划线
     */
    private static Pattern HUMP_PATTERN = Pattern.compile("[A-Z]");

    @Getter
    @Setter
    class FieldInfo {
        final String fieldName;
        final Class<?> fieldType;

        public FieldInfo(String fieldName, Class<?> fieldType) {
            this.fieldName = fieldName;
            this.fieldType = fieldType;
        }
    }

    private final Class resultClass;
    private boolean isInitialized;
    private final Map<String, FieldInfo> aliasFieldMap = new HashMap<>();

    public DOResultTransformer(@NonNull Class<T> resultClass) {
        this.resultClass = resultClass;
        isInitialized = false;
    }


    public T transformTuple(Object tuple[], String aliases[]) throws SQLException {
        Object result = null;
        if (!isInitialized) {
            initialize(aliases);
        }
        // 从构造方法进入
        try {
            result = resultClass.newInstance();
            for (int i = 0; i < tuple.length; i++) {
                final FieldInfo fieldInfo = aliasFieldMap.get(StringUtils.upperCase(aliases[i]));
                if(fieldInfo == null) {
                    continue;
                }
                BeanUtils.setProperty(result, fieldInfo.getFieldName(), tuple[i]);
            }
        } catch (Exception e) {
            String reason = new StringBuilder().append("Could not instantiate resultclass: ").append(resultClass.getName()).toString();
            throw new SQLException(reason);
        }
        return (T)result;
    }

    private void initialize(String aliases[]) {
        final Field[] declaredFields = resultClass.getDeclaredFields();
        for (Field declaredField : declaredFields) {
            // final 和 static 修饰的都不是 bean 字段
            if(Modifier.isFinal(declaredField.getModifiers()) || Modifier.isStatic(declaredField.getModifiers())) {
                continue;
            }

            // 字段名称和类型
            final String fieldName = declaredField.getName();
            final Class<?> fieldType = declaredField.getType();
            // 获取字段上的注解
            final Column columnAnno = declaredField.getAnnotation(Column.class);
            if(columnAnno == null || StringUtils.isBlank(columnAnno.name())) {
                // 无注解
                aliasFieldMap.put(StringUtils.upperCase(humpToLine(fieldName)), new FieldInfo(fieldName, fieldType));
            } else {
                // 有注解, 并且 Column name 不为 null
                aliasFieldMap.put(StringUtils.upperCase(columnAnno.name()), new FieldInfo(fieldName, fieldType));
            }
        }
        isInitialized = true;
    }


    /**
     * 驼峰转下划线
     */
    public static String humpToLine(String str) {
        Matcher matcher = HUMP_PATTERN.matcher(str);
        StringBuffer sb = new StringBuffer();
        while (matcher.find()) {
            matcher.appendReplacement(sb, "_" + matcher.group(0).toLowerCase());
        }
        matcher.appendTail(sb);
        return sb.toString();
    }


    public boolean equals(Object o) {
        if (this == o)
            return true;
        if (o == null || getClass() != o.getClass())
            return false;
        DOResultTransformer that = (DOResultTransformer) o;
        if (!resultClass.equals(that.resultClass))
            return false;
        return true;
    }

    public int hashCode() {
        int result = resultClass.hashCode();
        result = 31 * result;
        return result;
    }
}