【0】README 1）本文全文總結(jié)于 ?http://www.mybatis.org/mybatis-3/zh/statement-builders.html
【1】在Java代碼中來動態(tài)生成SQL代碼就是一場噩夢 1）problem+solutions： 1.1）problem：Java程序員面對的最痛苦的事情之一就是在Java代碼中嵌入SQL語句。這么來做通常是由于SQL語句需要動態(tài)來生成-否則可以將它們放到外部文件或者存儲過程中。正如你已經(jīng)看到的那樣，MyBatis在它的XML映射特性中有一個強大的動態(tài)SQL生成方案。但有時在Java代碼內(nèi)部創(chuàng)建SQL語句也是必要的。（干貨——事實上，在Java代碼中來動態(tài)生成SQL代碼就是一場噩夢） <pre name="code" class="java">String sql = "SELECT P.ID, P.USERNAME, P.PASSWORD, P.FULL_NAME, " "P.LAST_NAME,P.CREATED_ON, P.UPDATED_ON " + "FROM PERSON P, ACCOUNT A " + "INNER JOIN DEPARTMENT D on D.ID = P.DEPARTMENT_ID " + "INNER JOIN COMPANY C on D.COMPANY_ID = C.ID " + "WHERE (P.ID = A.ID AND P.FIRST_NAME like ?) " + "OR (P.LAST_NAME like ?) " + "GROUP BY P.ID " + "HAVING (P.LAST_NAME like ?) " + "OR (P.FIRST_NAME like ?) " + "ORDER BY P.ID, P.FULL_NAME"; 1.2）solutions）MyBatis 3提供了方便的工具類來幫助解決該問題。使用SQL類，簡單地創(chuàng)建一個實例來調(diào)用方法生成SQL語句。上面示例中的問題就像重寫SQL類那樣： private String selectPersonSql() {return new SQL() {{SELECT("P.ID, P.USERNAME, P.PASSWORD, P.FULL_NAME");SELECT("P.LAST_NAME, P.CREATED_ON, P.UPDATED_ON");FROM("PERSON P");FROM("ACCOUNT A");INNER_JOIN("DEPARTMENT D on D.ID = P.DEPARTMENT_ID");INNER_JOIN("COMPANY C on D.COMPANY_ID = C.ID");WHERE("P.ID = A.ID");WHERE("P.FIRST_NAME like ?");OR();WHERE("P.LAST_NAME like ?");GROUP_BY("P.ID");HAVING("P.LAST_NAME like ?");OR();HAVING("P.FIRST_NAME like ?");ORDER_BY("P.ID");ORDER_BY("P.FULL_NAME");}}.toString(); }
【2】SQL類 1）這里給出一些示例： // Anonymous inner class public String deletePersonSql() {return new SQL() {{DELETE_FROM("PERSON");WHERE("ID = #{id}");}}.toString(); }// Builder / Fluent style public String insertPersonSql() {String sql = new SQL().INSERT_INTO("PERSON").VALUES("ID, FIRST_NAME", "#{id}, #{firstName}").VALUES("LAST_NAME", "#{lastName}").toString();return sql; }// With conditionals (note the final parameters, required for the anonymous inner class to access them) public String selectPersonLike(final String id, final String firstName, final String lastName) {return new SQL() {{SELECT("P.ID, P.USERNAME, P.PASSWORD, P.FIRST_NAME, P.LAST_NAME");FROM("PERSON P");if (id != null) {WHERE("P.ID like #{id}");}if (firstName != null) {WHERE("P.FIRST_NAME like #{firstName}");}if (lastName != null) {WHERE("P.LAST_NAME like #{lastName}");}ORDER_BY("P.LAST_NAME");}}.toString(); }public String deletePersonSql() {return new SQL() {{DELETE_FROM("PERSON");WHERE("ID = #{id}");}}.toString(); }public String insertPersonSql() {return new SQL() {{INSERT_INTO("PERSON");VALUES("ID, FIRST_NAME", "#{id}, #{firstName}");VALUES("LAST_NAME", "#{lastName}");}}.toString(); }public String updatePersonSql() {return new SQL() {{UPDATE("PERSON");SET("FIRST_NAME = #{firstName}");WHERE("ID = #{id}");}}.toString(); }

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