Mybatis generator代码生成
背景
项目中使用Mybatis做持久层框架，但由于开发成员水平不一，写dao的时候，各有各的偏好，有时候还会写出带sql注入漏洞的代码。
出现sql注入漏洞，一般是#和$的区别没弄明白：
$ 直接把字符串原封不动的搬进sql，有sql注入的风险
# 是预留一个问号,作为参数插入的，即可通过预编译sql的方式避免sql注入
于是想使用Mybatis generator这个工具来统一生成代码（java bean，mapper，xml）
使用
Mybatis generator可以通过如下方式运行
- 命令行
下载mybatis-generator-core.jar，然后配置generatorConfig.xml文件，执行如下命令
java -jar mybatis-generator-core-1.3.7.jar -configfile generatorConfig.xml -overwrite
- IDE插件，run as
安装eclipse/idea插件
- 通过main方法执行
public static void main(String[] args) throws Exception {
List<String> warnings = new ArrayList<String>();
boolean overwrite = true;
ConfigurationParser cp = new ConfigurationParser(warnings);
Configuration config = cp.parseConfiguration(MainGenerate.class.getClassLoader().getResourceAsStream("generatorConfig.xml"));
DefaultShellCallback callback = new DefaultShellCallback(overwrite);
MyBatisGenerator myBatisGenerator = new MyBatisGenerator(config, callback, warnings);
myBatisGenerator.generate(null);
System.out.println("----done----");
}
问题及解决方法
分页问题
默认生成的xml是没有分页查询的，可通过
<plugin type="org.mybatis.generator.plugins.RowBoundsPlugin">
来实现分页，不过...
- 在低版本的generator插件里是不包含这个的。
- 使用这个插件生成分页代码后，会多一个selectByExampleWithRowbounds(XxxExample example, RowBounds rowBounds) 的方法，但是XxxMapper.xml文件中的selectByExampleWithRowbounds元素，可以发现select语句并没有使用limit 或者 rownum。
实际上RowBounds原理是通过ResultSet的游标来实现分页，容易出现性能问题
解决办法
可使用pagehelper来解决，See Github
除此之外，我们也可以通过自定义分页插件来解决
- Oracle插件
package com.yejg.mybatis.generator.plugins;
// 省略import
public class OraclePaginationPlugin extends PluginAdapter {
public boolean modelExampleClassGenerated(TopLevelClass topLevelClass, IntrospectedTable introspectedTable) {
PrimitiveTypeWrapper integerWrapper = FullyQualifiedJavaType.getIntInstance().getPrimitiveTypeWrapper();
Field begin = new Field();
begin.setName("begin");
begin.setVisibility(JavaVisibility.PRIVATE);
begin.setType(integerWrapper);
topLevelClass.addField(begin);
context.getCommentGenerator().addFieldComment(begin, introspectedTable);
Method setBegin = new Method();
setBegin.setVisibility(JavaVisibility.PUBLIC);
setBegin.setName("setBegin");
setBegin.addParameter(new Parameter(integerWrapper, "begin"));
setBegin.addBodyLine("this.begin = begin;");
topLevelClass.addMethod(setBegin);
context.getCommentGenerator().addGeneralMethodComment(setBegin, introspectedTable);
Method getBegin = new Method();
getBegin.setVisibility(JavaVisibility.PUBLIC);
getBegin.setReturnType(integerWrapper);
getBegin.setName("getBegin");
getBegin.addBodyLine("return begin;");
topLevelClass.addMethod(getBegin);
context.getCommentGenerator().addGeneralMethodComment(getBegin, introspectedTable);
Field end = new Field();
end.setName("end");
end.setVisibility(JavaVisibility.PRIVATE);
end.setType(integerWrapper);
topLevelClass.addField(end);
context.getCommentGenerator().addFieldComment(end, introspectedTable);
Method setEnd = new Method();
setEnd.setVisibility(JavaVisibility.PUBLIC);
setEnd.setName("setEnd");
setEnd.addParameter(new Parameter(integerWrapper, "end"));
setEnd.addBodyLine("this.end = end;");
topLevelClass.addMethod(setEnd);
context.getCommentGenerator().addGeneralMethodComment(setEnd, introspectedTable);
Method getEnd = new Method();
getEnd.setVisibility(JavaVisibility.PUBLIC);
getEnd.setReturnType(integerWrapper);
getEnd.setName("getEnd");
getEnd.addBodyLine("return end;");
topLevelClass.addMethod(getEnd);
context.getCommentGenerator().addGeneralMethodComment(getEnd, introspectedTable);
return true;
}
@Override
public boolean sqlMapDocumentGenerated(Document document, IntrospectedTable introspectedTable) {
XmlElement parentElement = document.getRootElement();
XmlElement paginationPrefixElement = new XmlElement("sql");
paginationPrefixElement.addAttribute(new Attribute("id", "Oracle_Paging_Prefix"));
XmlElement pageStart = new XmlElement("if");
pageStart.addAttribute(new Attribute("test", "begin != null and end != null"));
pageStart.addElement(new TextElement("select * from ( select row_.*, rownum rownum_ from ( "));
context.getCommentGenerator().addComment(paginationPrefixElement);
paginationPrefixElement.addElement(pageStart);
parentElement.addElement(paginationPrefixElement);
XmlElement paginationSuffixElement = new XmlElement("sql");
paginationSuffixElement.addAttribute(new Attribute("id", "Oracle_Paging_Suffix"));
XmlElement pageEnd = new XmlElement("if");
pageEnd.addAttribute(new Attribute("test", "begin != null and end != null"));
pageEnd.addElement(new TextElement("<![CDATA[ ) row_ ) where rownum_ > #{begin} and rownum_ <= #{end} ]]>"));
context.getCommentGenerator().addComment(paginationSuffixElement);
paginationSuffixElement.addElement(pageEnd);
parentElement.addElement(paginationSuffixElement);
return super.sqlMapDocumentGenerated(document, introspectedTable);
}
@Override
public boolean sqlMapSelectByExampleWithoutBLOBsElementGenerated(XmlElement element, IntrospectedTable introspectedTable) {
XmlElement pageStart = new XmlElement("include"); //$NON-NLS-1$
pageStart.addAttribute(new Attribute("refid", "Oracle_Paging_Prefix"));
// context.getCommentGenerator().addComment(pageStart);
element.getElements().add(0, pageStart);
XmlElement isNotNullElement = new XmlElement("include"); //$NON-NLS-1$
isNotNullElement.addAttribute(new Attribute("refid", "Oracle_Paging_Suffix"));
// context.getCommentGenerator().addComment(isNotNullElement);
element.getElements().add(isNotNullElement);
return super.sqlMapUpdateByExampleWithoutBLOBsElementGenerated(element, introspectedTable);
}
/**
* This plugin is always valid - no properties are required
*/
public boolean validate(List<String> warnings) {
return true;
}
}
- MySQl插件
package com.yejg.mybatis.generator.plugins;
// 省略import
public class MySQLPaginationPlugin extends PluginAdapter {
@Override
public boolean validate(List<String> list) {
return true;
}
/**
* 为每个Example类添加limit和offset属性已经set、get方法
*/
@Override
public boolean modelExampleClassGenerated(TopLevelClass topLevelClass, IntrospectedTable introspectedTable) {
PrimitiveTypeWrapper integerWrapper = FullyQualifiedJavaType.getIntInstance().getPrimitiveTypeWrapper();
Field limit = new Field();
limit.setName("limit");
limit.setVisibility(JavaVisibility.PRIVATE);
limit.setType(integerWrapper);
topLevelClass.addField(limit);
Method setLimit = new Method();
setLimit.setVisibility(JavaVisibility.PUBLIC);
setLimit.setName("setLimit");
setLimit.addParameter(new Parameter(integerWrapper, "limit"));
setLimit.addBodyLine("this.limit = limit;");
topLevelClass.addMethod(setLimit);
Method getLimit = new Method();
getLimit.setVisibility(JavaVisibility.PUBLIC);
getLimit.setReturnType(integerWrapper);
getLimit.setName("getLimit");
getLimit.addBodyLine("return limit;");
topLevelClass.addMethod(getLimit);
Field offset = new Field();
offset.setName("offset");
offset.setVisibility(JavaVisibility.PRIVATE);
offset.setType(integerWrapper);
topLevelClass.addField(offset);
Method setOffset = new Method();
setOffset.setVisibility(JavaVisibility.PUBLIC);
setOffset.setName("setOffset");
setOffset.addParameter(new Parameter(integerWrapper, "offset"));
setOffset.addBodyLine("this.offset = offset;");
topLevelClass.addMethod(setOffset);
Method getOffset = new Method();
getOffset.setVisibility(JavaVisibility.PUBLIC);
getOffset.setReturnType(integerWrapper);
getOffset.setName("getOffset");
getOffset.addBodyLine("return offset;");
topLevelClass.addMethod(getOffset);
return true;
}
/**
* 为Mapper.xml的selectByExample添加limit
*/
@Override
public boolean sqlMapSelectByExampleWithoutBLOBsElementGenerated(XmlElement element, IntrospectedTable introspectedTable) {
XmlElement ifLimitNotNullElement = new XmlElement("if");
ifLimitNotNullElement.addAttribute(new Attribute("test", "limit != null"));
XmlElement ifOffsetNotNullElement = new XmlElement("if");
ifOffsetNotNullElement.addAttribute(new Attribute("test", "offset != null"));
ifOffsetNotNullElement.addElement(new TextElement("limit ${offset}, ${limit}"));
ifLimitNotNullElement.addElement(ifOffsetNotNullElement);
XmlElement ifOffsetNullElement = new XmlElement("if");
ifOffsetNullElement.addAttribute(new Attribute("test", "offset == null"));
ifOffsetNullElement.addElement(new TextElement("limit ${limit}"));
ifLimitNotNullElement.addElement(ifOffsetNullElement);
element.addElement(ifLimitNotNullElement);
return true;
}
}
生成的xml不是覆盖旧文件，有时还有重复的段
问题原因在于：
在IntrospectedTableMyBatis3Impl.getGeneratedXmlFiles方法中，isMergeable值被写死为true了。
GeneratedXmlFile gxf = new GeneratedXmlFile(document,
getMyBatis3XmlMapperFileName(), getMyBatis3XmlMapperPackage(),
context.getSqlMapGeneratorConfiguration().getTargetProject(),
true, context.getXmlFormatter());
而MyBatisGenerator.writeGeneratedXmlFile方法中使用到该属性了。代码如下：
if (targetFile.exists()) {
if (gxf.isMergeable()) {
source = XmlFileMergerJaxp.getMergedSource(gxf, targetFile);
} else if (shellCallback.isOverwriteEnabled()) {
source = gxf.getFormattedContent();
warnings.add(getString("Warning.11", targetFile.getAbsolutePath()));
} else {
source = gxf.getFormattedContent();
targetFile = getUniqueFileName(directory, gxf.getFileName());
warnings.add(getString("Warning.2", targetFile.getAbsolutePath()));
}
} else {
source = gxf.getFormattedContent();
}
解决办法
方法一：可直接修改源码，把isMergeable写成false
方法二：拿到GeneratedXmlFile对象，通过反射把isMergeable改成false
// 可以在前面自定义的Plugin中，sqlMapGenerated方法中拿到GeneratedXmlFile对象
public boolean sqlMapGenerated(GeneratedXmlFile sqlMap, IntrospectedTable introspectedTable) {
try {
java.lang.reflect.Field field = sqlMap.getClass().getDeclaredField("isMergeable");
field.setAccessible(true);
field.setBoolean(sqlMap, false);
} catch (Exception e) {
}
return true;
}
注释问题
默认的注释完全没什么用，不如自定义注释，把数据库表字段的注释作为bean字段的注释
解决办法
public class MyCommentGenerator implements CommentGenerator {
private Properties systemPro;
private boolean suppressAllComments;
private SimpleDateFormat dateFormat;
public MyCommentGenerator() {
super();
systemPro = System.getProperties();
suppressAllComments = false;
dateFormat = new SimpleDateFormat("yyyy-MM-dd");
}
/**
* 生成java model的类头上的注释
*/
@Override
public void addModelClassComment(TopLevelClass topLevelClass, IntrospectedTable introspectedTable) {
if (suppressAllComments) {
return;
}
topLevelClass.addJavaDocLine("/**");
StringBuffer sb = new StringBuffer();
sb.append(" * ");
sb.append(introspectedTable.getRemarks());
sb.append(" [");
sb.append(introspectedTable.getFullyQualifiedTable().toString().toLowerCase());
sb.append("]");
topLevelClass.addJavaDocLine(sb.toString());
topLevelClass.addJavaDocLine(" * @author " + systemPro.getProperty("user.name"));
topLevelClass.addJavaDocLine(" */");
}
/**
* 添加字段注释
*/
@Override
public void addFieldComment(Field field, IntrospectedTable introspectedTable, IntrospectedColumn introspectedColumn) {
if (suppressAllComments) {
return;
}
StringBuilder sb = new StringBuilder();
sb.append("/** ").append(introspectedColumn.getRemarks().replace("\n", " ")).append(" */");
field.addJavaDocLine(sb.toString());
}
// 省略了其他方法
}
不过在使用的时候发现通过
introspectedColumn.getRemarks()
获取到的注释为null，此问题可通过修改xml配置文件来处理
<jdbcConnection driverClass="oracle.jdbc.driver.OracleDriver" connectionURL="jdbc:oracle:thin:@127.0.0.1:1521:YEJG" userId="XXX" password="XXX">
<!-- 针对oracle数据库 -->
<property name="remarksReporting" value="true" />
<!-- 针对mysql数据库 -->
<!-- <property name="useInformationSchema" value="true" /> -->
</jdbcConnection>
序列问题
其实这算不算什么问题，xml配置一下就可以了
<table tableName="users">
<property name="useActualColumnNames" value="true" />
<generatedKey type="pre" column="SERIAL_NO" sqlStatement="select users_seq.nextval from dual"></generatedKey>
</table>
这里需要注意下，generatedKey不要写在property前面了，mybatis generator对顺序有要求的。
字段命名方式问题
数据库表字段是USER_ID形式，生成的bean的字段变成userId形式
解决办法
可在generatorConfig.xml中添加如下配置
<property name="useActualColumnNames" value="true" />
不过这么一来，bean中的字段就都变成大写的了，期望生成user_id的形式，可通过修改源码来解决
// DatabaseIntrospector#getColumns，把column_name先toLowerCase处理一下
introspectedColumn.setActualColumnName(rs.getString("COLUMN_NAME").toLowerCase());
关于代码
以上代码已上传到Github
