手把手教你写一个java的orm（四）下
实现首先我们要根据User.java拿到所有的表的字段个名称，和对应的值。就是上一篇写到的：EntityTableRowMapper[*]拿到字段和class属性的值Map<String, Field> columnFieldMapper = entityTableRowMapper.getColumnFieldMapper();insertColumns = new ArrayList(columnFieldMapper.size());for (Map.Entry<String, Field> stringFieldEntry : columnFieldMapper.entrySet()) { Field field = stringFieldEntry.getValue(); Object value = EntityUtils.getValue(entity, field); if (value == null) { continue; } insertColumns.add(stringFieldEntry.getKey()); insertColumnValues.add(value);}这里有两个变量：insertColumns：sql中的字段名。insertColumnValues：sql中的字段对应的值。
[*]生成插入的sql：StringBuilder builder = new StringBuilder();int size = insertColumns.size();builder.append("INSERT INTO ").append(getTableName()).append(StringUtils.SPACE);builder.append(StringUtils.append("( ", StringUtils.join(insertColumns, ", "), " ) "));builder.append("VALUES ");for (int i = 0; i < insertCount; i++) { builder.append("( "); String[] repeat = StringUtils.repeat("?", size); builder.append(StringUtils.join(Arrays.asList(repeat), ", ")); builder.append(" )"); if (i != insertCount - 1) { builder.append(StringUtils.COMMA); }}builder.append(";");
[*]生成的结果：//userUser user = new User();user.setId(10);user.setCreateDate(new Date());user.setAge(20);user.setMark("ceshi");user.setName("heiheihei");//sqlINSERT INTO user ( name, id, create_date, age, mark, status ) VALUES ( ?, ?, ?, ?, ?, ? );//value
[*]现在可以拿着生成的sql和值去执行啦～jdbcTemplate.update(sql, insertColumnValues.toArray());
感谢分享 感谢分享
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