【Mybatis】Mybatis对clob字段的处理

【前篇】

【纲领】

用jdbc处理clob字段，存入时需要创建Clob对象，然后以setString(1,"...")的方式存入；取出时需要把字段内容先放入Clob对象里，然后要用个char数组将内容一段段读出来，再拼接成文字。一言以蔽之，有点麻烦！

在Mybatis的帮助下，Clob字段可以和varchar2，nvarchar2字段等同视之，一律映射为String类型，其中繁琐工作就由Mybatis代行就好了，便利很多。

【表结构】

create table test03(
    id number(3),
    content clob,
    primary key(id)
)

映射的类：

public class Article {
    private long id;
    private String content;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }
}

注意Article的content成员和表Test03的字段content的对应关系。

【Mapper类】

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;

@Mapper
public interface Test03Mapper {
    Article findById(long id);

    int addOne(@Param("id") long id, @Param("content")  String content);
}

【Mapper.xml】

<?xml version="1.0" encoding="UTF-8" ?>
DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="Test03Mapper">
    <select id="findById" resultType="Article">
        select * from test03 where id = #{id}
    select>

    <insert id="addOne">
        insert into test03 (id,content)
        values (#{id},#{content})
    insert>
mapper>

【存入代码】

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;

public class MybatisClobWriter {
    public static void main(String[] args) throws Exception{
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory =
                new SqlSessionFactoryBuilder().build(inputStream);

        try (SqlSession session = sqlSessionFactory.openSession()) {
            Test03Mapper mapper = session.getMapper(Test03Mapper.class);

            String content=readFromFile("c:\\hy\\yylj.txt");
            mapper.addOne(2,content);

            session.commit();
        }
    }

    static String readFromFile(String path) throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(path), "UTF-8"));

        String line = null;
        StringBuilder sb=new StringBuilder();
        while( ( line = br.readLine() ) != null ) {
            sb.append(line+"\n");
        }
        br.close();

        return sb.toString();
    }
}

【取出代码】

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.InputStream;

public class MybaticClobReader {
    public static void main(String[] args) throws Exception{
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory =
                new SqlSessionFactoryBuilder().build(inputStream);

        try (SqlSession session = sqlSessionFactory.openSession()) {
            Test03Mapper mapper = session.getMapper(Test03Mapper.class);
            Article a = mapper.findById(2);
            System.out.println(a.getContent());
        }
    }
}

【代码下载】

 https://files.cnblogs.com/files/heyang78/RestAccessEs220226.rar?t=1645882753

 END