Java获取Mybatis动态生成的sql接口实现

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目的：利用mybatis动态生成sql的能力返回可执行的sql，但并不会执行。 场景：需要生成复杂的sql供其他程序执行

1. 编写xml： SqlGenarate.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="com.jason.bi.data.sql.generate">

    <select id="getSql">
        SELECT
            a,
            b
        FROM
            `table_name`
        WHERE
            field1 = #{field1Value} AND field2 = #{field2Value}
    </select>

</mapper>

2. 定义接口

import io.swagger.annotations.ApiOperation;

import java.util.Map;

/**
 * @author: jason
 * @Date: 2022-01-04
 */
public interface SqlService {

	@ApiOperation(value = "动态生成sql")
	String generate(String sqlId, Map<String, Object> paramMap);
}

3. 实现接口 sqlId = namespace + '.' + id 如SqlGenarate.mapper.xml中getSql对应的sqlId即为：com.jason.bi.data.sql.generate.getSql paramMap为参数，paramMap.put("field1Value","abc"),paramMap.put("field2Value","efg"),

import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.ParameterMapping;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Map;

/**
 * @author: jason
 * @Date: 2022-01-04
 */
@Service
public class SqlServiceImpl implements SqlService {
	@Autowired
	private SqlSessionFactory sqlSessionFactory;

	@Override
	public String generate(String sqlId, Map<String, Object> paramMap) {
		//获取执行sql
		Configuration con = sqlSessionFactory.getConfiguration();
		//传xml文件中的 需要执行的id编号,如： com.jason.bi.data.sql.generate.getSql
		MappedStatement s = con.getMappedStatement(sqlId);
		BoundSql bSql = s.getBoundSql(paramMap);
		//获取到sql中封装的参数的数量
		List<ParameterMapping> paramValues = bSql.getParameterMappings();
		return getExecuteSql(bSql.getSql(), paramValues, paramMap);
	}

	/**
	 * 生成可执行sql
	 *
	 * @param sql         获取的sql
	 * @param paramValues 动态参key
	 * @param map         动态参valur
	 * @return
	 */
	private String getExecuteSql(String sql, List<ParameterMapping> paramValues, Map map) {
		while (sql.indexOf("?") != -1 && paramValues.size() > 0) {
			String paramName = paramValues.get(0).getProperty();
			String paramValue = map.get(paramName).toString();
			String value = "";
			if (paramValue instanceof String) {
				value = "'" + paramValue + "'";
			}
			sql = sql.replaceFirst("\\?", value);
			paramValues.remove(0);
		}
		return sql;
	}
}