前言

实现基于postgresql，springboot，spring mvc和mybatis-plus，原理是将List＜T＞转为JSONArray类型，数据库对应字段为json类型，即可完成存储。

实现

建表如下：

create table test.image_info (
   id serial PRIMARY key NOT null,
   image_address text    NOT NULL,
   image_owner text    NOT NULL,
   download_times int8  default 10,
   authorized_user json,
   is_deleted int8 NOT null
);

创建List处理器，ArrayTypeHandler.java：

package org.sample.handler;

import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.MappedJdbcTypes;
import org.apache.ibatis.type.MappedTypes;

import java.sql.*;
import java.util.Arrays;
import java.util.List;

/**
 * 
 */
@MappedJdbcTypes(JdbcType.ARRAY)
@MappedTypes(Object.class)
public class ArrayTypeHandler extends BaseTypeHandler<Object> {

    private static final String TYPE_NAME_VARCHAR = "varchar";
    
    private static final String TYPE_NAME_INTEGER = "integer";
    
    private static final String TYPE_NAME_BOOLEAN = "boolean";
    
    private static final String TYPE_NAME_NUMERIC = "numeric";
    
    private static final String TYPE_NAME_LONG = "bigint";

    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, Object parameter, JdbcType jdbcType) throws SQLException {
        Object[] arrayObject;
        if (parameter instanceof List) {
            arrayObject = ((List) parameter).toArray();
        } else {
            arrayObject = (Object[]) parameter;
        }
        Connection conn = ps.getConnection();

        if (arrayObject.length > 0) {
            String typeName = TYPE_NAME_VARCHAR;
            if (arrayObject[0] instanceof Integer) {
                typeName = TYPE_NAME_INTEGER;
            } else if (arrayObject[0] instanceof String) {
                typeName = TYPE_NAME_VARCHAR;
            } else if (arrayObject[0] instanceof Boolean) {
                typeName = TYPE_NAME_BOOLEAN;
            } else if (arrayObject[0] instanceof Double) {
                typeName = TYPE_NAME_NUMERIC;
            } else if (arrayObject[0] instanceof Long) {
                typeName = TYPE_NAME_LONG;
            }
            Array array = conn.createArrayOf(typeName, arrayObject);
            ps.setArray(i, array);
        } else {
            ps.setArray(i, null);
        }


    }

    @Override
    public List<Object> getNullableResult(ResultSet resultSet, String s) throws SQLException {
        return getArray(resultSet.getArray(s));
    }

    @Override
    public List<Object> getNullableResult(ResultSet resultSet, int i) throws SQLException {
        return getArray(resultSet.getArray(i));
    }

    @Override
    public List<Object> getNullableResult(CallableStatement callableStatement, int i) throws SQLException {
        return getArray(callableStatement.getArray(i));
    }

    private List<Object> getArray(Array array) {
        if (array == null) {
            return null;
        }
        try {
            return Arrays.asList((Object[]) array.getArray());
        } catch (Exception e) {
        }
        return null;
    }
}

有entity如下：

@Data
@NoArgsConstructor
@AllArgsConstructor
@EqualsAndHashCode(callSuper = false)
@TableName(value = "test.image_info ")
public class ImageInfo implements Serializable {


    /**
     * ID
     */
    @TableId(value = "id", type = IdType.AUTO)
    private Long id;

    @TableField(value = "image_address")
    private String imageAddress;

    @TableField(value = "image_owner")
    private String imageOwner;

    @TableField(value = "download_times")
    private int downloadTimes;

    @TableField(value = "authorized_user", typeHandler = ArrayTypeHandler.class)
    private JSON authorizedUser;

    @TableField(value = "is_deleted")
    private int isDeleted;

}

核心实现过程：

        // 创建entity
        List<String> finalAuthorizedUsers = authorizedUsers;
        ImageInfo imageInfo = new ImageInfo();
        imageInfo.setId(0L);
        imageInfo.setImageOwner(username);
        imageInfo.setAllowDownloadTimes(imageDownloadTimes);
        imageInfo.setAuthorizedUser(finalAuthorizedUsers);
        imageInfo.setIsDeleted(IsDeletedEnum.NO.getCode());
        imageInfo.setCreateTime(new Timestamp(System.currentTimeMillis()));
        imageInfo.setCreateUser(username);
        imageInfo.setUpdateUser(username);

		// 插入数据库
        int insert = imageInfoServiceMapper.insert(imageInfo);