解析Mapper.xml

在 XMLScriptBuilder 的parseScriptNode()方法中解析每个sql语句。

package org.apache.ibatis.scripting.xmltags;
public class XMLScriptBuilder extends BaseBuilder {
  public SqlSource parseScriptNode() {
    MixedSqlNode rootSqlNode = parseDynamicTags(context);
    SqlSource sqlSource;
    if (isDynamic) {
      sqlSource = new DynamicSqlSource(configuration, rootSqlNode);
    } else {
      sqlSource = new RawSqlSource(configuration, rootSqlNode, parameterType);
    }
    return sqlSource;
  }
  protected MixedSqlNode parseDynamicTags(XNode node) {
    List<SqlNode> contents = new ArrayList<>();
    NodeList children = node.getNode().getChildNodes();
    for (int i = 0; i < children.getLength(); i++) {
      XNode child = node.newXNode(children.item(i));
      if (child.getNode().getNodeType() == Node.CDATA_SECTION_NODE || child.getNode().getNodeType() == Node.TEXT_NODE) {
        String data = child.getStringBody("");
        TextSqlNode textSqlNode = new TextSqlNode(data);
        if (textSqlNode.isDynamic()) {
          contents.add(textSqlNode);
          isDynamic = true;
        } else {
          contents.add(new StaticTextSqlNode(data));
        }
      } else if (child.getNode().getNodeType() == Node.ELEMENT_NODE) { // issue #628
        String nodeName = child.getNode().getNodeName();
        NodeHandler handler = nodeHandlerMap.get(nodeName);
        if (handler == null) {
          throw new BuilderException("Unknown element <" + nodeName + "> in SQL statement.");
        }duan
        handler.handleNode(child, contents);
        isDynamic = true;
      }
    }
    return new MixedSqlNode(contents);
  }
}

上面parseDynamicTags方法中判断sql语句中是否有“${}”，如果有一个地方含有动态语句，则这个sql就是动态sql，即为DynamicSqlSource类型，否则为RawSqlSource类型。

解析静态sql

package org.apache.ibatis.scripting.defaults;

public class RawSqlSource implements SqlSource {

  private final SqlSource sqlSource;

  public RawSqlSource(Configuration configuration, SqlNode rootSqlNode, Class<?> parameterType) {
    this(configuration, getSql(configuration, rootSqlNode), parameterType);
  }

  public RawSqlSource(Configuration configuration, String sql, Class<?> parameterType) {
    SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);
    Class<?> clazz = parameterType == null ? Object.class : parameterType;
    sqlSource = sqlSourceParser.parse(sql, clazz, new HashMap<>());
  }

  private static String getSql(Configuration configuration, SqlNode rootSqlNode) {
    DynamicContext context = new DynamicContext(configuration, null);
    rootSqlNode.apply(context);
    return context.getSql();
  }

  @Override
  public BoundSql getBoundSql(Object parameterObject) {
    return sqlSource.getBoundSql(parameterObject);
  }

}

由上面代码可以看出，对于静态sql，其在构建RawSqlSource对象时，就会解析sql。例如将”#{}”替换为”？”。

在解析时，对于标签例如：WhereSqlNode、IfSqlNode 以及含有${}的TextSqlNode等都是动态DynamicSqlSource，文本内容保持不变，例如IfSqlNode的sqlSource为”name = #{name,jdbcType=VARCHAR}”,而TextSqlNode中包含${}时sqlSource为”id = ${id}”，其他静态TextSqlNode则会将”#{}”替换为”？”。